I once had a friend who was very promiscuous since she was 13. She saw nothing wrong with having over 20 something sexual partners by the time she was 17. i never called her a whore, slut or anything similar. why? because i realized something was wrong. She had self esteem issues and family problems. She still has issues. I have has known several girls like this. And all of them had underlying issues. One was being abused. Instead of calling your friend names, why wont you try to find out what is wrong with her? I dont think a 13 year old should be having sex, but if she is as promiscuos has you claim there could be reasons behind it.