☆.A.
Well, I may be in the minority, but I think being with "better" girls might inspire her, not discourage her. Kind of true in all sports--you play with those better to GET better, right?
As for Little Miss Snot Nose? At eight, I think it's time for all kids to learn that EVERY other kid has a right to be where they are, classroom, gymnastics, etc. And eight is old enough to learn to tolerate the people they don't care for. The other kid has also paid her money and has a right to be there, imo.
Good luck!