I agree with carmalee - you can only be victim in all this, if you let yourself be one. Put the boot on the other foot - you start laying down some rules for her, like "butt out of my life". You have joint tenancy so it's not as if it's her house, she can't tell you who can come to the house - you could say "X is coming tonight, I want you to go out".
It might be a joint tenancy, but have you explored how to break it, so you can move out and move on, or buy out your ex in some way?