Yes, JLC, we've faced the same issue with music.
Our DD's private music teacher has been one of her best allies. Do private dance lessons exist? If so, maybe a private teacher would help your DD to progress at a faster pace by herself. At least she would be allowed to grow artistically, instead of stagnating. However, it may not help the frustration of being in a group ensemble that is too slow for her, and you may not be able to change that. We've run into that, too.
How old is your DD? You may want to explore a summer program for the arts. PM me if you're interested in that possibility.
