By the time you catch up, the two fillies are already mid-conversation below one of the windows.

“Well,” Diamond Tiara rolls the map back up again, “According to this, that’s the best way in. It offers the most cover.”
“So we don’t even need it anymore? Wasn’t this a waste of time?” Silver Spoon, completely aware that you’re there, points at you without looking. “It’s not like we had to wait for her.”
“It pays to be prepared.” Diamond Tiara tosses the map into the bushes. “Now help me up.”
“Excuse me? It’s my birthday-” Silver Spoon pauses to judge the position of the moon, “Technically today! You give me a boost!”
Diamond Tiara scoffs, “Well that’s not going to happen.” She points to you. “Give us a boost, and we’ll pull you in from inside.”

Can they really not make that jump? You’re positive you can. This could prove an ideal opportunity to leave those two behind. But, if they can make it inside, or even if they can’t, they’ll likely find a way to sabotage you. Or at least try.

Aunt Bon-Bon says kids are always very melodramatic. Lyra says that most adults forget how dramatic it is being a kid.

Double-cross sounds a little harsh. You just want to get away from them.

A simple enough question. You ask.

Berry Pinch forces through a yawn before answering. “Black mail; why else would anypony be here?”
“I was invited!” Zipporwhill excitedly replies.

Diamond Tiara and Silver Spoon return, looking annoyed.
“Aren’t you two done yet?” Diamond Tiara looks square at Berry Pinch, “I thought you said this wasn’t going to take very long.”
Berry Pinch walks towards Diamond Tiara, shoves the clipboard into her chest, and starts walking away, “I’m going home.”
“What?!” Silver Spoon exclaims, “If you leave now we’ll-!”
“You’ll what?” Berry Pinch replies over her shoulder, “Map is in your writing-style. I was never here.”
Silver Spoon rushes over to Diamond Tiara and gasps at the map. Diamond Tiara waves Berry Pinch away, “Let her go. She knows this isn’t over.”
Zipporwhill flies over, looking worried, “Where is she going?”
“Don’t care,” Diamond Tiara replies coldly, rolling up the map, “Just like I don’t care where you go. But it won’t be with us.”
Her wings stop beating and Zipporwhill lands slowly, “But… But you said we were having a sleepover!”
“Tsk. I don’t remember ever saying that.” Diamond Tiara puts a hoof to her mouth and turns to Silver Spoon, “Do you remember me ever saying that?”
Silver Spoon taps her chin, “Something about coming over for the night. Nothing about sleeping. Nothing about staying.”
Zipporwhill’s lowerlip quivers and you can see tears forming in her eyes.
“Too bad,” Diamond Tiara brushes past her, “But don’t worry. We’re sure you won’t get in too much trouble when you get home.”
“Come on, Zipporwhill,” You hear Berry Pinch call back. Evidently she turned around and came back. “You can spend the night at my house.”
Zipporwhill quickly flies over to Berry Pinch, her voice still shaken, “But-but won’t your mom be super-angry?”
“Trust me, she won’t care,” Berry Pinch replies and the two disappear into the night.

After watching this scene, you turn around to berate the two bullies for their horrible behavior, but they’ve already walked away toward one of the castle windows.

Berry Pinch is… different. Ms. Cheerilee says she’s gifted. Aunt Bon-Bon says she’s mature for her age. Lyra calls her “abnormally intelligent”. She can act like a normal filly when she’s playing, but beyond that she’s very serious, very careful, and very smart. You have to wonder what forced her to be here tonight.

From Berry Pinch’s perspective, it must look like you’re working with Diamond Tiara and Silver Spoon, instead of for them. You try to explain, but she interrupts you.

“It doesn’t matter now; it’s too late for you to back out.” Berry Pinch stops what she’s doing to look you in the eye. “But you’d better get away from them as soon as possible. You might think everything is sorted out. That it’s fair. But all they’re doing is gaining more and more clout to hang you with. And once they have enough,” She turns back to her clipboard and resumes writing, “You’ll never be free again.”

You gulp hard with a shiver. It suddenly feels a lot colder outside than it did before.

You’re just a kid! You can’t incapacitate an adult guard! You do tell her everything else, though.

“Don’t worry your little head over it, Little Liza,” Diamond Tiara waves a hoof in dismissal.
“Yeah,” Silver Spoon chimes in. “Secrets never remain secret to us for very long.”
“No kidding…” Berry Pinch says with a dejected yawn.
“And it’s not like we’ll be splitting up,” Diamond Tiara puts a hoof around Silver Spoon. “If we leave you alone, you might blow our cover.”
You see Zipporwhill zip over to comment, “I am so very excited for our upcoming adventure!”
“Yeah,” Diamond Tiara rolls her eyes.
“Whatever,” Silver Spoon does the same.

Zipporwhill gives a wide smile and returns to looking into the windows while Diamond Tiara and Silver Spoon take a few steps away, seemingly to talk in private. Berry Pinch glances over at you and stares for a long moment before going back to her drafting.

“Dancing with the devil tonight, aren’t you?”

Diamond Tiara seems to be waiting for you to ask, so you do.

“Oh, it’s really quite brilliant.” She rubs a hoof on her chest and glances down to admire it, “A true testament to my intellect.”
“Except it was my idea…” Berry Pinch mutters under her breath.
“And I picked you to think of something, so that makes it my idea. Daddy says that’s delegation.”
Berry Pinch can only roll her eyes in response.
“As I was saying,” Diamond Tiara turns back to you, “The help is mapping out the back of the castle and guessing at how the rooms connect. It won’t be perfect, but together with our knowledge it should be enough to get us around.” Diamond Tiara leans in close, “FYI, they don’t know what we’ll be looking for. If it is true, the fewer ponies that know, the better.”

You can’t argue with that. Getting caught in another dimension isn’t like getting caught sneaking a cookie. You’d get in at least twice as much trouble!

You have room enough to pack some water. Good thing Lyra buys bottled water. She doesn’t like the taste of tap. You can’t tell the difference.

Another dimension is no place for a dog, so you put out some extra dog food and leave Simple behind. Hopefully you won’t be gone too long. Or somepony comes to investigate.

With nothing more to do, you head out early toward Princess Twilight’s Palace. The sun has completely set by now, but the moonlight is just bright enough to find your way along the empty roads. When you reach the outskirts it appears you’re alone at first, but you see a light shine in the darkness on one side of the castle. As you approach, you realize it was Silver Spoon’s glasses; she was using them to reflect the moonlight as a signal.

“About time you got here,” Silver Spoon puts her glasses back on and adjusts them, “We were starting to think you weren’t going to show!” She turns away and walks along the side of the castle, under the well lit windows. You start to mention that you’re fifteen minutes early, but you’re too exhausted from dealing with these two to argue.

You and Silver Spoon reach the backside of the castle to find Diamond Tiara and, oddly enough, Berry Pinch and Zipporwhill. Zipporwhill is buzzing about looking in the windows and talking to Berry Pinch, who seems to be writing something. Once you get close enough, you can tell Zipporwhill seems to be having the time of her life, but Berry Pinch looks tired and miserable. There are clear bags under her eyes and she yawns two or three times every minute.

Diamond Tiara walks over to “greet” you, “So hard to find good help, and on such short notice. Here’s hoping this little vacay of yours is worth the trouble, for your sake.”

You pace around for a minute or two. You aren’t really sure what to do next. There’s still time to do… something, you’re just not sure what it would be. You could go ahead and meet up with Diamond Tiara and Silver Spoon. But that probably involves waiting, and you’re a little antsy.

If you can’t think of anything, you won’t really have much choice.

You’re not really comfortable with carrying around a weapon. But hey! Who says a knife has to be a weapon?! It’s a great survival tool! You can cut stuff with it and-… Well, you don’t really have much in the way of survival skills. You doubt Diamond Tiara or Silver Spoon do either. Maybe you could find somepony who does?

By cutting an empty paper tower roll and using some a bunch of tape to reshape it, you craft a Portable Knife Holder! You combine that with a Kitchen Knife to make a Safe-For-Travel Knife and put that in your bag! You might not have any survival skills, but you’re as crafty as a slice of cheese!

… That… That probably would have been funnier if Kraft cheese existed in your world.

Unfortunately you already used your +1 foresight to make the Stealth Slippers. With no more points to use at the moment, you’d need significant direction to make anything else.

You’d make more Stealth Slippers, but there aren’t enough belts in the house. You know because you checked.

It couldn’t hurt to offer. But Diamond Tiara is pretty interested in that whip, even if she doesn’t want to show it. You’d need to get her attention away from it first.

…

You inhale deeply and yell your aimless, senseless question in an accent you have little understanding of. Diamond Tiara’s ears curl down and she winces. Evidently you can yell really loud!

“What is wrong with you, you spazz?” Diamond Tiara forces out in a slow, pained tone. You apologize and present your idea: to take her and Silver Spoon on a once-in-a-lifetime trip to another world!

“You really think there’s a portal to another dimension in Princess Twilight’s castle?” You nod and Diamond Tiara pauses for a moment to think. A sly smile makes its way across her face, “Counter proposal: Silver Spoon and I help you on your silly little "quest”, and if there isn’t a portal, we get the whip and you have to be our servant in school for a week.“

That’s rough. You agree before the full weight of what you’re agreeing to settles in. That would be one loooong week.

"Good.” She tosses the whip onto Aunt Bon-Bon’s bed,  “I’ll go pull some strings. Meet me by the road to the palace in an hour.” She leaves without another word.

Well, things seem to be coming together. Anything you could do in an hour?

You lead Diamond Tiara to Aunt Bon-Bon’s room (because it’s not Lyra’s room). Immediately Diamond Tiara finds the whip laying on the floor. You couldn’t decide if you should take it or not and never put it back.

Diamond Tiara walks over and nudges the whip, “Nightmare Night was how long ago?”

You explain that it’s not a costume prop. That it’s a real leather whip.

She scoffs and picks up the whip, “Yeah, right. That’s not even possible. If this was real it would have to be ancient. They haven’t made…” She stops and looks at the whip closer, sliding her hoof across the whip’s braids. “What… is this made of? I’ve never seen this material before. This can’t really be…” She catches herself before she sounds too interested, “It’s still dumb, even if it is real. But I suppose I could gift it to Silver Spoon as a novelty.”

There is no way Aunt Bon-Bon would allow Diamond Tiara or Silver Spoon to have her whip. The moment she returns she’ll make them give it back. And when she does… Tartarus will look comfortable compared to what they’ll drag you through.

But… It would get them to leave you alone, for now at least. What choice do you have? It’s not like you could just invite them to go to another dimension with you for Silver Spoon’s birthday present.

What do you do?

This is a bad idea.

You lead Diamond Tiara up to your room and start to show her some things she could give Silver Spoon. She refuses each one with bored, single-word answers like: “No. Lame. Boring.” You hear a page turning behind you and turn around to find her reading your diary!

She glances at you from around the book, “Truffle? Really? Not that I’m surprised, but I think you could do better.”

This was a horrible idea.

That’s sort-of what this is about. Lyra and Bon-Bon disappeared and you’re trying to find them. Things have… gotten off track a bit…

You resist the urge to deliver a haymaker to Diamond Tiara’s face, for now.

You feel your face turn flush. You… didn’t realize it was a bear’s…

You have to figure this is a present she would be giving publicly, with adults around. You’re not sure if either of them would be interested in the movie, but Diamond Tiara would know better than to accept that.

Diamond Tiara is staring at you. You haven’t answered her yet.

You attempt to be a smart-rump, but as soon as you start to turn your head, Diamond Tiara whips you back around. A little painfully at that.

“She’s not going to tell anypony without my O.K. But that doesn’t mean I won’t. Another slip up like that and I’ll be spreading around more than just your delinquent desires.”

You swallow hard with a “gulp”.

Technically speaking, your parents are rich too. Maybe more so than Diamond Tiara’s; you don’t know. They just didn’t raise you to be a brat. Though she does seem to have an allowance, which you lack.

You comment on how glad you are to be spending some time with Diamond Tiara. Her face twists into clear disgust, but she doesn’t reply.

Strangely enough, you both arrive at Aunt Bon-Bon’s house. Continuing with this act you open the door and allow her entry. While she looks around you unleash Simple and he runs off.

“This place is filthy,” Diamond Tiara scowls. “Don’t you have a maid or anything?”

You tell her that Aunt Bon-Bon and Lyra can’t afford something like that, and she just shakes her head.

“Whatever. Look, you don’t want to get in trouble. So let’s make a deal.” Diamond Tiara turns away and her hateful, controlling demeanor seems to relax. For the moment, she almost looks like a normal kid.
“As you know, Silver Spoon’s birthday is tomorrow. I was going to get her something great, but I already spent my allowance, my back-up allowance, and my emergency allowance. Daddy says he won’t give me anymore money until this Saturday!”
She turns around, clearly upset. “Can you believe that?! I thought he was going to pay for it! Why should I have to pay for her present with my money anyway?! It’s so unfair!”
The outburst passes and she sits on her haunches and looks down. “Now I don’t have anything to give her at her party… I can not just not give her anything. You’ll help me, right?”

Unfortunately not an option, as that’s implied. The pair have set up a kind of mandatory silence when it comes to their actions. Anypony that dares break the chain will have their secrets and embarrassing moments revealed one after another until they cave. Then they’re forced to share secrets to them about others, furthering their control. It’s incredibly cruel, but not something any one pony can fight against. Maybe one day everypony can stand against them both at once and end the cycle, but that’s obviously not today.

You toss away any remaining scrap of pride or self-worth, drop to your haunches and knees, and with tears in your eyes beg for them to not tell. There’s an almost evil glint in Silver Spoon’s eyes, and you feel that she’s ready to enact her ultimate revenge and strike you down at your weakest moment. But it doesn’t remain long.

Diamond Tiara approaches you and lifts up your head, “Poor, poor Liza. You must think us awful for bringing you to such a lowly state.”
Silver Spoon snickers, “Yeah.”
You’re surprised to find Diamond Tiara’s hoof extend to help you up, “You should come with me. Just the two of us. We’ll hang out. Play some games. I’ll show you I’m not such a bad pony.”
“Yeah…! Wait, what?!” Silver Spoon’s face is awash with confusion. Admittedly, yours probably is as well.

Diamond Tiara puts her foreleg around your neck and turns to Silver Spoon, “We’ve hung out together since school. I don’t have to foalsit you all day, do I?”
Silver Spoon is completely speechless. If not for the terrible feeling that this is somehow going to get much worse for you, you’d almost be enjoying yourself.
Diamond Tiara rolls her eyes, “Oh stop. It’s not like I won’t see you tomorrow at your birthday party. I just need to spend a little time with Little Liza here. You understand, of course.” She turns around, taking you with her, and you both walk away without so much as a goodbye. But under her breath, you hear Diamond Tiara whisper to you, “That’s right. Keep walking. Don’t look back and don’t say a word.”

There’s that sense of dread again.