LW1: Your friend is...I don't even have words. A child is not an object or "gift" you get for someone, especially before you leave them, and especially someone who is abusive. It's sounds like she's trying to buy an easy exit from the relationship with the currency of a little girl. You are correct that having a  child 24/7 is different than just visits, and it is likely that once he no longer has your friend to target, he will switch to targeting this little girl. A child should NEVER have to be exposed to that. Your friend will merely be switching the child from one unstable parent to another. Your friend's husband may be abusive, but she's definitely no peach either, and I think you'd be right to warn those involved. You'll just have to accept that when you do, your friend will probably no longer be your friend - if that's really a loss, given what you've said.