S.A.
I think you are on target with the "let the kids handle it themselves" however it is difficult to do that when you see your child being picked on. My daughter is in the 6th grade and we have allowed things to work themselves out in the past. Of course we give her lots of wise counsel at home (as it seems you are doing). The tween years are a lot tougher for girls than we imagine it to be or perhaps tougher than we remember. I recommend reading the book "Queen Bees and Wanna Be's" in addition to "Reviving Ophelia". These two references might give you more insight to what is really happening and how to manage things. I DO think it is a very good idea to quietly (not to make it a public ordeal and thereby compound the problem) let the teacher(s) know what is happening so she/they can keep a watchful eye on the situation...JUST IN CASE (as it seems the ring leader has a personality disorder of some sort in addition to OBVIOUSLY being VERY jealous of your daughter). Make certain that your daughter knows she should feel pity (although I know that is the LAST emotion she probably can muster right now) for her agitating school mate as she must be very unhappy with things in her life at this time. Misery loves company as they say.