Deception and Insight rolls are a thing. Also, others might successfully reason with her. It might be only Minx's approach specifically that doesn't work.

As for doing what the dungeon wants... Aurelia was already on to something when the plushies animated. She was starting to find clues, and that still is a perfectly fine avenue to pursue once you get out of the cribs. Also, you think you need to regress and baby talk to get out, but what if that's not the only way?

You didn't even utilise all assets you had when you were fighting. The adamantite maul for one, would have absolutely rekt the plushies, as it auto-crits objects, so even with the resistance to bludgeoning damage, they would have gone down easily. And if the whole party committed to the fight, you could have hacked them up one by one if you ganged up on them.

I am perfectly willing to accept Minx or the party decision isn't always right and the others are going to be part of things, I'm well aware how things work in a table top RPG. I'm planning on waiting on lord fluff, like you said. And the other players can do what they want, I merely asked for a heads up for next time in my post.

The issue is Seela is useful only to convince to get out of the cribs and is unable to be reasoned with in any other manner. The whole information gathering is moot when we are told up front she doesn't have to tell us the truth or lie, which means we can ask all we want and have no IC reason to trust it. Getting her to let us go or convincing her we're not a threat is blindingly simple like you said, baby talk and regression.

It just seems like the options in this whole section boil down to do as the dungeon wants, anything else is going to get you punished.

Lastly, if this was a solo adventure for Minx and Minx alone, I would definitely make sure that she can solve each and every situation of her own and tailor the encounters to your preferences. But there are 3 other player characters in this, whom I have to let be part of this. Even if they choose to satisfy their kinks.

The road block is that you insisted that only through combat can the previous situation be solved. Thus the whole party ended up locked up. The plushies would have let you out once you were all cooperating. You could have even moved on to the next room without issue if you didn't attack. You chose to attack. They responded, and you bit off more than you could chew. It happens to adventurers in D&D time to time. You don't always win. One path closes, another opens. Seela only appeared because you lost, and she's not a road block, she's your ticket out of your current predicament - if you find out how to use it.

Well, currently you're the only one trying to talk to her, and the rest barely got a chance to chime in yet. And well, she lived a millenium in isolation, carriying the burden of being the last uncorrupted being left of her race. OF COURSE she is disconnected. What else could she be?
She's even dropping hints. She's lonely, she likes taking care of others, she obviously loves to talk, and she's curious, although vary. Can you for a moment maybe see what the others make of that, if you insist Minx doesn't give in the slightest or even attempt to play on those blindingly obvious traits of Seela? I'm not talking about begging. You could talk her for information, try to convince her that you're no threat, let the others have a word with her, I'm not going to spoonfeed all your options, figure it out, or let Dialga and the others figure it out. I can accept if Minx doesn't want to give in the slightest and not apologize even if she doesn't mean it, because it's her character, but then you need to also accept that her approach won't always be the correct one, and sometimes she'll rely on the rest of the party to get out of a situation.

I really don't mean to tell you how to DM, but Seela is not doing very much to be anything but a road block. She doesn't understand the fact jumping people with random plushie animals tends to make them fight back, and her comparisons are stretching things at best, and seem disconnected at worst, plus asking them questions is now a useless endevour since she just told them she doesn't have to tell them the truth. So like... what are we supposed to do here? Just sit and beg to be let go?

Heh, I imagine. She's just very, very opposed to getting younger and being totally helpless. We'll see if that changes over time.

She doesn't have to, either.
Funny enough, behind any of the other doors, she would have found encounters fitting a hack and slash situation XD But you picked the least threatening door, so you get the least threatening enemies :P

Not trying to be difficult in character with Minx by the way, she's just not going to surrender right away.

If we're waiting on someone, we can get shopping and such done now so when they do come back, we don't waste time advancing the story since anyone who isn't around can just retroactively have shopped when they come back.
Course, it's perfectly fine to just wait, was just a suggestion.