L.M.
I agree with M H that some kids do better in individual activities. Group activities are great at teaching team work and cooperation. However, these can be acheived through different means (i.e. play dates, game nights...). Maybe doing these types of group activities in a smaller setting will lead to more success. Also, it would give you the chance to guide the interactions for positive results. You are on the right track allowing her to try activities that she is interested in. Maybe you can guide her toward more individual type activities (i.e. music lessons, tennis, swimming...). It doesn't sound like the issue is quitting, but learning how to deal with group situations. Kudos to you for continuing to give her these opportunities.