This sounds like myself at 14 ! First question... Is the her father in her life? The other question is,is there any indication she could be using drugs? Maybe, sit her down and have a heart-to-heart talk...let her know that she's the most important thing in your life.Let her know that she can tell you anything.But, when she does ,remember to be non-judgmental and try not to freak out about the stuff she may say.Her low self-esteem stems from somewhere,or,from something that has happened to her.Ask her why she feels the way she does.Ask her what you can do to help her feel better about herself.Maybe,even have her go talk to a professional... because at that age she's in, sometimes it's hard to talk to parent about stuff.Sometimes, having an unbiased view into one's life is the best.Remember, being a teen is really hard and this could just be a phase she's going through.But, my best advice is, to be involved as much as you can in her life.Maybe, set a day aside for just the both of you... a little retail-therapy never hurts.Get her invovled with activites like an art class, or karate... something that will build some self- confidence.Everything works itself out.... good luck!