My best friend is an alcoholic, and she is dying of liver failure right now. I am glad I was able to reconnect with her last winter and have a few months with her while she was sober.
Your friend is lost. If I can offer one piece of advice, it would be to have compassion. Now, that doesn't mean you have to put up with her craziness or any cruelty, just know that underneath it all is a sick person. And chances are she knows this about herself too.
It kills me that I am losing my friend to alcoholism, that it could have been prevented, but that time has since passed and now there is no hope anymore for her finding sobriety. But I sit with her each day, holding her hand, wishing her peace. I know if she could have a do-over, she'd not make the same choices this time around. I know this is not her legacy she wanted to leave.
Detachment is good, but do it with love and prayers that your friend finds her way soon, and doesn't go down the path mine has.