You know, leaving aside for the moment Maddie's brittle front finally shattering, There's still the question of
why did Rose teleport them to the dungeon?. Maybe it's the only place she can teleport people (because it was only included as a security mechanism), sure, but why would OldTrace have put that limiter on it? (Speaking of which, I'm pretty sure that limit would've been lifted too). There are plenty of other places that would've made more sense to teleport them to - the lobby, their rooms,
the infirmary - that I'm seriously questioning why they got teleported to the dungeons. It does make me wonder just how much resentment Rose has built up and if we're about to see her lash out with it now that she isn't held back.
Then there is the question: Assuming that
is Rose we saw silhouetted there (Something I doubt, partly due to the hair, partly due to ears), does projection-Rose know what happened to flesh-and-blood-Rose? Are they separate consciousnesses? If they were, are they still? They must have been the same at one point (even if projection-Rose was a 'copy' of flesh-Rose) because projection-Rose has been acting like an older real-Rose the entire time.
back to Maddie: tbh I don't find her sudden switch all that surprising. We already know she
really doesn't like being called little, so we know that she caught a lot of flak for that growing up, and in a culture like that of the Basitins, it'd be systemic, not just childhood bullies (esp since she doesn't really have the same protection of being the King's Daughter that she would in any other monarchy). That is not a happy childhood to grow up in, and that tends to result in people forming strong but brittle fronts to hide what they really feel.
Maddie has been holding a (metaphorical) mask for so long that I expect it's practically a part of her. She's been proving that she can handle it, that she
is tough enough despite her size, and she got a nice big boost to her how she thought she was doing after fighting Seraphina. Now the day after that success, she gets the [censored] kicked out of her and not only does that tear up the emotional hill she just ascended, but the idea that she can't handle it, that she isn't tough enough, that she can't fight, dug a pit for her to fall into from that hill. Add in the pain and blood she's coughing up (I'm still not entirely convinced by the "I'm a basitin, I'll be fine" bit) and the entire front she's been putting up just shattered like a stained glass window with a giant stone Lizardfolk statue thrown through it. Until she manages to rebuild it (or manages to overcome her prior experiences and go from a ceramic-encased ball of peach-and-strawberry-strength person to a personality/sense-of-self more like an old tree; one that isn't a mask hiding her true feelings, one that bends but doesn't break) she's going to be very vulnerable.
edit: also, the bars on that cage are definitely wide enough that they can just slip out