Tinkerbell is brought back with the audience clapping/kids saying they believe in the play/book. But she dies after Wendy leaves anyways, simply because she has reached the end of her natural life (in the book it's said that she was a newborn almost when Peter fetched Wendy, and she dies after she leaves. The kids actually stay on Neverland for a few weeks. Fairies are kinda like mayflies in the books)

I didn't like how Julia Roberts plays a fully happy Tink. The worse parts of her persona are omitted fully. Plus, she doesn't have any fey logic. In short, I found the Tink in Hook to be way too human. And, also, that growing thing was just weird.

And yeah, Peter would read her body language. But also "invent" (he assumes she agrees with him when she really doesn't). Peter is Chaotic Neutral in the first books and he's a pure kid. That comes with the bad side of childhood.