Hello Rose, I'm right there with you. I'm in tears reading your posts, been through all of this with my eldest daughter and just like you, I knew the advice I was given was right, just as surely I knew that it wouldn't work on my daughter. My daughter did not get as violent as yours, but I'm absolutely certain she would have done if I'd tried to get tougher with her. She was beyond that.
Since you don't mention a husband or partner, would I be right in assuming that her father isn't in the picture, but that he (or someone) has treated her in some damaging way in the past? That's what went wrong with my daughter, she had a rotten abusive father who'd hurt her by the time I found out about it and rescued her. My other two children are not like her, although the second one has the same father he hadn't got around to hurting her yet before I found out. She will never be like her sister, I can tell without any shadow of a doubt.
Here's what happened. We had a year of hell, basically. She did as she liked without reference to us. We gave up trying to restrict her movements. She would have gone out anyway. We asked if she would at least be so good as to tell us where she was. Because we'd laid off her with regard to her movements, she surprised us by doing so. If I was worried I'd phone her on her mobile. I couldn't control her behaviour by withdrawing anything - she voluntarily gave up an allowance, lifts, etc so that we wouldn't be able to exert any influence on her. She was rude and abusive, which we tried to ignore or simply reply reasonably. I often felt too worried to sleep, hurt, broken hearted, very much abused by my child. Many times I felt like giving up. But I could always see inside this behaviour the angry, wounded little girl who'd been utterly let down and rejected by her father, and I knew I couldn't do the same. I had to be there for her till she got over it. I had wonderful support from other mumsnetters.
She slowly got worse over age 14 - 15 and then from 15 - 16 gradually (as I like to term it) rejoined the human race. What I did in that time was critical - I could have pushed her further away if I hadn't been patient and careful.
A turning point was the day I offered to move house so that we could find a place with a separate bedsit of some kind for her. That way she could continue her studies with our support but live a life without our interference. Some have said this was too much of a sacrifice for us, but we were planning to move anyway around this time, and we could see that there was a real possibility of her leaving altogether if we didn't bend over backwards for her.
We haven't yet moved, but will in the next few months. Our house is only almost ready to sell now. She has calmed right down and is looking forward to her own space as soon as we can give it to her. I think it really made her stop and evaluate things when we offered to do this for her, no longer could she make the old excuses that we didn't genuinely care about her, that we were doing it all to look right.
She's learned that we'll do our best for her no matter what. I don't think she's yet reached being mortified and sorry for all the hurtful things she's done, but I'm confident that she will one day. It took her father years to mess her up so much, and it's taken me years to try and pull her back from the brink. (My daughter did take an OD) But that's what mums do, isn't it?
Sorry this is so long, and hope it is some help.