Hi ggg, I spotted this thread this morning and have only just had time to come back to it and read some of the posts.
I just want to say I have been through the exact same things with my DD1 who appears to be exactly the same age as your DD as well. I don't think anyone who hasn't experienced this could possibly understand how impossible it is to control the behaviour of such an individual. I always feel that most mums out there are wondering why the hell I didn't put a stop to it, but they somehow manage to circumvent everything you try until you are left with three choices, seemingly. 1 put up with it, 2 Turn your back on her or 3, use brute force.
And because none of these three choices are acceptable you become completely powerless to be the good parent you want to be, it's like living in hell. You don't sleep at night wondering if your child has gone out/is downstairs stealing something/trashing your house/taking drugs/talking with someone unsuitable on msn...every tiny noise awakens you. Nothing you say to her is right, however harmless and conciliatory she will find fault and pick an argument. She will lie in your face and make you feel like the guilty one. You wonder how this child could ever have come out of your body. I just want you to know I understand.
I feel parenting DD1 has taken years off my life. She has left home (of her own accord) and immediately taken up with her father who was denied contact by the court because of his unsuitability. She is walking a tightrope where she could end up really damaged, and she can't see it and can't heed advice. There is nothing more I can do except pick up the pieces one day in the future when she comes back hurt.
I hope you find a way to handle it all without losing your sanity - I'm so sorry I don't have advice for you as I have struggled and failed with precisely the same problem. All I can do is tell you I understand and I am here for you if you want to talk.