She obviously has some growing up to do. I suspect that as she matures a bit, she'll look back on her own behavior and feel worse about that than the remark she received in turn.

I think rock chick is right when she says "we only end up hurting ourselves."
I can recall only two times in my life when I deliberately said something with the intention of hurting someone. Both were in response to a nasty thing they had said to me and I wanted to get even. I immediately regretted saying them and I've no doubt it was more painful for me than it was for them. I was eight years old at the time.