I remember as a kid really looking forward to an activity I'd always loved. When I got there, I realized that most of the kids my age hadn't signed up this year. The only ones who had were not at all the kind I would hang out with. That's my first guess about what's happening.
But I also echo a pp that it's possible something bad happened and she won't tell you. I have a kid who came home from college mid-semester anxious and stressed. She said she didn't know why she felt that way all of a sudden, but over time it became clear that there was much more to the story than what I heard at the very beginning.