I dropped someone like that recently. I lost a handful of friends in the process, but I reestablished some friendships with people I'd lost trying to keep that person's resentment at bay. The aftermath wasn't half as bad as I was expecting, but I think that's part of what makes it so hard to leave behind the manipulative "friend" in the first place.

I'm much happier for it now and I wish you all the strength in the world to get out of that bad situation.