I looove Ai's character building so much! While it is realistic to believe Ai broke down, I also won't be surprised if she never did, at least, since leaving for Tokyo and becoming an idol. It's quite hard to explain. To hit such a low low in your life you break and experience a hysterical high, pretending and gaslighting yourself into being okay, then suddenly getting hit by the harsh truth that you've lost your ability to feel properly and lack the ability to reciprocate the affection people you've come to care about give you, and you don't quite understand what's going on anymore – like you've been going with the flow your entire life and now huge waves are taking you to a place you're unfamiliar with and afraid of but you don't know what else to do because you never tried going against the tide... I don't think it's entirely impossible.