I hope she comes around too. Perhaps point her in the direction of this board? I'm not sure if that would compromise your willingness to share (and if it does then I wouldn't), but she needs to understand how screwed up and dangerous the situation is.
If she fears what your AS will do to her if the child is taken away, she should be able to call anonymously so AS will have no idea who has reported her. Even if she has her suspicions that it is you guys who are actually sticking up for the child, what can she really do? Nothing. She can go crazy in her own hell because it's her terrible, awful decisions that got her in this mess. Perhaps losing the one thing that actually means something to her will waken her up a bit. I hope so anyway.
Either way, if your friend does call CPS and only tells "the facts," it is possible that it will launch an investigation, so don't give up all hope yet. I'm sorry you're having to deal with this and I feel really sorry for that little kid too...Thank you for not giving up.