I think I remember reading something about this before, but not all the details. Could be someone else though.

If she's not willing to move out, I'd be renting somewhere else. Give her a month's notice and find somewhere you can go in the new year. I know it won't be as good for you financially, but emotionally you need it. It isn't on promising something then flat out not doing it and making it harder for the other person. (Can you hear me, mother?)