I agree with tigerlily about the counseling. She seems to have a great view about this and you should listen to her since she bettered her life and raised 3 very decent daughters--that I'd sure be proud to have! I do have 2 of my own and am definately proud....but have a long, long time before I have to deal with this issue since my 7yr. old son thinks girls are the enemy
and my 3 yr. has a while, of course.
I also want to add that she needs to be taken away from these friends of hers...as soon as possible. At this age they are more her drive and influence most likely and mom has to fight for her well-being b/c she sounds very self-distructive.
I too was promiscuous and had deep, dark reasons for it. I luckily met my husband and we cared enough about eachother and life(not to mention the son we made after only 3 mos.) to start living right. He's a wonderful guy and he saved my life. But for her she's so young that she needs some "tough love". Her mom needs to take drastic measures to keep her away from the bad influences so her daughter can come to her senses. Daughter may hate mom at first, but-God willing-she'll thank her later!
Also, communication is soooo important. She needs to ask her daughter in a concerned way(the way you communicate is delicate, not just what you say but how you say it is important--ppl respond differently to different tones, I'm just figuring this out!) why she is acting this way. Non-judgemental. If the daughter shuts down at least mom got her thinking and opened a door for when daughter feels bad about her behavior and needs a confidant(sp?). She needs to keep this openminded, still parental role with her. Focus on the sleeping around minimally and the deep reasons for it a lot. I hope my view helps! Best of luck.
Parenting is the most selfless, delicate job in the world and mom has to realize there's trial and error involved, so NEVER give up!