We have always let our kids decide if they want to do a sport or activity or not. However once they say they one to do they have to keep that commitment. As for the tryout have her go. There maybe some fear of not making the team that is keeping her from wanting to go. I know my DD2 is talented at softball and acting but resists doing tryouts or auditions for fear of failing. So I truly feel it is part of my job as a parent to help her confront those fears.