Adult Henry goes time-travels back and visits his childhood quite a bit. His daughter Alba is also a time-traveller who goes back and visits her past. But we never see her as anything older than a child, just as an older child going back to visit her younger childhood and events before she is born.
So why do we never see teen or adult Alba? It's a pretty strong indication of the possibility that - despite her limited abilities to control her time travel, and the family/professional support structure for it she has that her father didn't - she succumbs to some of the dangers of showing up naked in a random place and time, and doesn't survive to be an adult.
There's also the possibility that a cure for time travel is found and she takes it. But somehow this seems less likely to me.
Though I never thought of this from the book before seeing the movie, I don't think there's anything in the book that specifically says Alba survives to adulthood. Thought the book does have one incidence of Henry traveling much further forward in time and visiting Alba's mother Clare as an old woman, which diverts us from the fate of Alba.