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.

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.

Even knowing they won’t take it, you offer them free candy. They don’t surprise you.

Diamond Tiara scoffs, “Candy? You think you can buy our silence with candy?”
“If that’s the best you’ve got, I think revenge would taste a lot sweeter…” Silver Spoon seems to be relishing this opportunity.

At least this proves they aren’t above forms of bribery. In fact, that’s probably what they were after all along. But they’re rich. You’d have to offer something with a different kind of value. Something you can’t just buy or find.

You unceremoniously (another big word) turn around and start to walk away. But you don’t get far before you hear them both behind you.

“Uh, hellooo?!” Diamond Tiara calls after you. “Aren’t we forgetting something?”
“Yeah!” Silver Spoon joins in. “Did you suddenly think we weren’t going to tell?”

Oops. You forgot why you even stomached talking to them for that long. You still need to convince them to not tattle on you.

You’ve never met anypony by that name, at school or otherwise. You’re also eight and have never seen The Brady Bunch. Why even ask this right now?

You decide to just tell the truth, or at least some of it. The pair seem less interested in this than before. Less because they don’t believe you, and more because they don’t care.

Diamond Tiara rolls her eyes when you finish, “If some smudged-up, old mirror is so important to you, why don’t you just knock?”
“Yeah, they’re giving tours of the castle today,” Silver Spoon adds. “Of course, we were on the first tour.”
“And would you look at the time? They might have finished for the day.”
“Wouldn’t that be a shame if Little Liza had to wait until next Tuesday?”

They both grin at each other. They’re right though! Princess Twilight was supposed to start giving tours of the castle every Tuesday! But with it being this late, they’re probably done for the day. You can’t wait a week! If they’ve been on a tour of the castle, they could probably help you navigate. This would make their help even more valuable if you sneak in. That is, if you can figure out how to convince them.

On the other hoof, you could just try knocking. Or maybe somepony on good terms with Princess Twilight could help you get in. Do you even know anypony like that?

You begin to explain the potential value in place as a criminal, using your own family’s heritage as an example. You discuss the Bohun family’s ancestry as successful pirates and how they practically built half of Canterlot! You’re interrupted pretty early on.

“Oh my gosh,” Silver Spoon turns to Diamond Tiara. “She’s really serious.”
Diamond Tiara shakes her head, “Wow, Liza. You really are a psychopath.”

The two are clearly unimpressed. In fact, they almost look worried. Not what you were going for. Maybe a different approach would work better?

You pick a direction at random and run with Simple like there’s an axe-swinging killer chasing you! Not the most level-headed thing to do, but if anypony planned to catch you, they’d have to catch you first!

Perhaps being led subconsciously, you finally slow around the schoolhouse. It’s after hours and there’s nopony here. Or at least, so you thought. Two unfortunately familiar voices spring up around you.

“Did you hear that?”
“Did I ever!”
“Breaking into a princess’s castle?”
“Haven’t you heard, Di? It’s always the quiet ones.”

Diamond Tiara and Silver Spoon step out from behind bushes on either side of you. They begin to encircle.

“I must say,” Diamond Tiara starts, “I didn’t think you had it in you.”
“Me neither,” Silver Spoon snidely adds on.
Diamond Tiara lifts a hoof to her mouth, as though she’s thinking, “Why, breaking into a castle? That’s just so utterly-”
“Criminal?” A sly smile creeps across Silver Spoon’s face.
Stifling a chuckle, Diamond Tiara continues, “Now now, we wouldn’t want Little Liza to lose her cool again. I mean, with nopony around, she might get hurt this time.”
“Oh but Di, we can’t just keep this to ourselves. This is treason!”
“You are so right! It’s our civic duty to inform Princess Twilight of a possible attempt… on her very life!”
“Poor Little Liza.” Silver Spoon turns to Diamond Tiara, “How long do you think she’ll get?”
“Why, they’ll probably lock her up and throw away the key.”
“I meant the guard, Di. Not her parents!”

They both laugh hard and you feel tears coming on. You punched Silver Spoon once and ever since they’ve been calling you a criminal. Everypony knows how much trouble you got in for that too. They know, and rightly so, that you’d never do that again. No threat or insult would hold any weight here. If they tell on you, your plans are completely shot. You’re totally at their mercy. And they have little of that to give.

On the other hoof, when you first changed your name to Liza, they were the first to start using it. They’ve never excluded you from anything they didn’t exclude everypony else from. And of all the kids in Ponyville, they are by far the most resourceful. And if you’re going to break into a castle, you’ll definitely need some help.

What do you do? What do you say?

You have to figure this is probably an inside joke or reference that Lyra would get. You aren’t even sure what it stands for. Chocolate Quilted Coconut? Can’t Quit Chasing? … You can’t think of anything else that starts with a Q. Wordsmith you are not.

In your excitement you ask the gray mare how to sneak inside the palace, without realizing what a horrible idea that was until it’s too late.  She immediately stops petting Simple, stares at you while taking a few steps back, and flies off. But not before cycling back around to deliver a letter to that mailbox you were blocking. Neither rain nor sleet, nor mischievous fillies evidently.

There is now a clear crowd of ponies watching you and whispering to each other. You should go. Somewhere. Anywhere. Now!

You skip formalities and just ask her if she’s seen Bon-Bon. A little surprised, she looks down at you, thinks for a moment, and shakes her head. You then ask if she’s seen Lyra, although you expect a similar answer. She pauses for a moment to think again, then tilts her head as though she’s now thinking harder. She suddenly jumps, widening her stance as she lands, and nods to you. She’s seen Lyra!

You ask her when the last time she saw her was, which prompts her to begin pantomiming (which is a big word for a filly your age). She puts her back up to a wall and begins inching her way toward a corner, stopping to look around like she’s watching for somepony following her. As she does this her mail bag, thankfully held on with a belt, wiggles and sways, but nothing falls out. She eventually reaches the corner and slides around to the other side. Though you follow her from the street, it seems she’s done performing and backs off of the building, which was somepony’s house. A few other ponies are watching both of you at this point.

When she returns to your side, she points high and off in the distance, in the clear direction of Princess Twilight’s palace.

That might take a while, and you might lose her. But, with faith in your heart you patiently wait for your opportunity.

… She dips behind a building and you lose sight of her completely… Well that sucks! So much for waiting your turn! You angrily think about what else you were taught in school that might be false, when you hear something land behind you. You turn around to find a gray pegasus, looking especially wall-eyed, contently gazing past you. Curiosity gets the better of you and you turn to see what she’s… well, mostly looking at. It appears you’re standing in front of a mailbox, effectively blocking it. Now’s your chance!

Aunt Bon-Bon says one of the neighbors hate us and you aren’t supposed to talk to them. Something about a leaf blower? Unfortunately, you don’t remember which one, so you’re not sure who you’re not allowed to talk to. Of course if push comes to shove… But better go with the alternative first.

You take Simple outside, along with the things you packed, and begin looking for the local delivery pony. As it just looks like you’re walking a dog, no pony pays much attention to you. It’s not long before you find a gray mare with a blond mane flying through the sky, descending to deliver something to a house, and then off again. She’s pretty fast. At one point you get close, only for her to soar over several houses to another street. Should you run to chase her? Try to get her attention? Would those seems suspicious? You’re trying to keep a low profile, after all.

Hmm… These are good points too. Lyra, as nice as she is, has always been sort of secretive. She probably wouldn’t have told anypony. And Aunt Bon-Bon has always been a… Well, overprotective. She definitely wouldn’t have just left. Almost definitely…

What if… What if she was foalnapped?! And the foalnapper took her hat that she never wears to make it look like she left willingly! That’s… Really dumb…

… Maybe she left… But she didn’t know she’d be gone for this long? Either way if she didn’t leave a note she probably wouldn’t have told anypony either…

You start to think about who might have saw one of them. They didn’t just vanish. They had to have trotted out the door and went somewhere, right? Who could have seen them? Maybe somepony who spends a lot of time outside?

In her defense, it’s not exactly something you weren’t aware of. You’ve just never seen one that particular… shape.

You haven’t! But that’s a good idea! Or, it would be if it didn’t involve a child willingly approaching a dentist. That’s like trotting up to your natural predator. Not out of the question, but certainly out of your comfort zone.

Lyra is pretty good friends with… what was her name? Derpy? Ditzy? … Dinky? No wait, that’s her daughter… Bubbles…? We’ll just call her Miss if we find her.

You also seem to remember Lyra talking with Berry Punch a few times. Golden Harvest too. Lyra knows lots of ponies. But, between your aunt and her roommate, that’s at least four you could choose from.

You search Bon-Bon’s room not expecting much, but are surprised with what you find. In a briefcase in her closet you find a whip. It’s definitely not a prop either, which makes it very cool! It’s a little long and heavy for a pony your size, though. You aren’t sure yet if you should take it.

Something even more important catches your eye. Bon-Bon has always had this old, tan hat hanging from a hook on her wall next to her closet. But all that’s left is an imprint on the wall where it used to be. She might have known ahead of time she was leaving and took it with her. Not enough to prove anything is wrong, but it’s a start.

In Lyra’s room you find… something you’d probably get in trouble if you asked about. You cautiously put it back exactly as you found it and decide to forget about ever searching her room. Ever again.

After looking around the house, and with a little imagination, you’ve managed to fashion something stealthy! By using some belts and a few wash cloths you’ve created Stealth Slippers!

…

It was a really dumb idea, but it’s actually been working incredibly well! Your hooffalls are so quiet you can’t even hear them! Unfortunately, as your bottom discovered, they also make you a little slide-y, and they take a while to put on. You’ll have to know in advance that you want to use them.

You are aware of a friend of Lyra’s that you’ve heard her talking to, but you’ve never seen him.

This is a very important idea! There’s definitely a lot of different ways to go about this, and sneaking around is certainly one of them. You’d have to be more specific, though. What, in a standard household, could be used to be more stealthy?

Regardless, you gain +1 foresight!