Like other said: unless her curvature has a Cobb’s angle higher than 20degrees, it is best to go for a conservative treatment. Being active and doing alot of sports will be the main goal here, but ofcourse she should include some specific stretching of the concave side and strengthen the convex side. But your doctor and physiotherapist should be able to guide you trough the process without any problem, after all it is a quite common issue.
I don’t see why it should hamper her performance. In the contrary, if she keeps to her strengthening regimen and looks after herself, she’ll probably have a stronger core than most athletes out there.
Just my (physiotherapystudent) two cents 