I don't think there is a quick fix, and particularly in this case, where I think some is just emotional development that she doesn't have yet (or has in some areas that differ from other kids smile ) you have to continue to do what you are doing. Continue to speak with her about responses and keep listening to her, make sure she knows it is okay to speak up for herself (especially that one can be respectful and speak powerfully at the same time - very important for all kids but especially for girls IMO), maybe find some books that talk about bullying (in the broad sense) and kindness and why children might act that way.

Good luck, Cat