Question

Yes it says at that in the first movie, and the book. Neither of which this movie acknowledges exist though. They made there own history up for it so I don't know if there belief as to her powers increasing in strength would play any role in this production.

It doesn't specify if her powers grew stronger or if she gained more as she grew up, but I think I remember Rainbird talking to someone about this and saying something about her powers being so strong as a child and speculating about how much more powerful she might be now.