Start documenting everything you know about. If you ever know that she is passed out, call CPS to check on the 10 year old. Keep advocating for this child - she is an innocent victim that has been taken hostage by your sister's addiction.
I would talk to everyone I could think of to try to help this child. Everyone. Attorneys, AA, CPS, Social workers, hospital staff, police. Keep working on it. I know others will be along to give you more ideas.
I'm sorry you're going through this, but as you know there is not much you can do about your sister. You can find a way to get that child out of there, though.