You are probably right in saying that those girls parents may deny it all if confronted with.But do they even know about what their girls are upto?I mean girls are that malicious at this tender age,I shudder thinking how toxic they will be in their adulthood and imagining how much trauma they will heap on innocents. Non intervention of those parents and non correction of those girls behaviours is angering me so much.I feel for you ,how much time and energy you are needing to put into this,but you have to for your own daughter's sake.I admire you for that.