My heart and prayers go out to you because I remember how badly I wanted my son to "see the light" and set his life straight.
What I learned was that he was on his own journey, one that had good periods of sobriety and dramatic periods of relapse. I learned that I could not control the path he would choose, so could only pray for him and trust that wherever life took him was where he was supposed to go to learn his own lessons. Life has taught me that there is often a gift in even their worst moments because that is often what brings them to their knees and helps them decide to change.
One thing I think I would do if I were you is to contact child services and let them know that the child is safe with you.
I'm sorry for your pain, and hers, and hope that life brings you both better days ahead.
Hugs