My daughter is 15 and I have gone through and continue to go through these things as well.
I have the same relationship with my EX-w as you. Basically none and am fine with that.
I don't agree you need to tell your ex-w. I think you need to be a rock for your daughter, sometimes just listening, sometimes maybe a little input,sometimes teaching a little DB and validating to her to help her deal with people. This has worked for me and my daughter comes to me often and we discuss it.
The more she understood that I wouldn't try to fix things the more open she is. Girls at that age are brutal. Also understand your daughter may have been involved more than what she let on.
I think how you deal with her will help her deal with the other girls. My daughter has made the comment that she has learned much from watching me interact with her mother right after Bomb day and that it has helped her. They know way more and learn more than what you think.
