Dalila,
I have not gotten there yet but I know it's around the corner....my little girl has just made herself known to me and she is hurting, but on some level i know my teenager is too. It is my little girl who dissociates a lot and my teenager who cuts and sometimes drinks wine and rebukes authority and so on.
I have a teenage son and two older sons. I think you can begin to parent your teen by imagining what you would say to any teenage girl you cared about....hmmm...As a teacher, I know they need lots of validation because they may be experimenting with adult roles and are unsure of themselve....just a thought.
Good luck, be good to yourself...I look forward to hearing about your progress because I'm right behind ya; but my little girl needs some more attention first.