My daughter likes dancing very much, but she is in the third grade. Even if she doesn't go to the third grade, I won't let her go, because dancing has no way out, because of this.
You should let her go. This is her hobby, and learning to dance is not bad.
Nowadays, many parents force their children to study, not only to exercise, but also to be admitted to art schools after studying well. It is also good for her to go out by herself, otherwise I hope it will help you in the future.