Well, I might be waaaaaaaaayyyyyyy off here, but it almost sounds like she is trying to shock you into reacting , when she tells you these things. most people do their thing (drink, be promiscuous , etc) without telling their parent. it is almost like she is saying, "watch, she wont be able to do anything. she is frozen with fear. i am in CONTROL!
she could get in a wreck, kill someone or herself, get raped, get pregnant, get a disease, etc, etc.
i would insist she get help or get out. take away the things that you provide that enable her to do these self destructive things.
she may be an alcoholic, or she may not. but she is definately living a dangerous life, and seems to be in need of help. kids dont need us to be friends, they need us to provide guidance and the safety that comes from having boundaries. she seems very much like a little child who has had too much power, and her actions scream "help", in my opinion.
act now, dont be afraid of her reactions. how could it get worse?