Screwed over (again). What should I do?

The best thing you can do is accept the situation and walk away. If you tell the ex what this guy said about her, she is going to confront him, and then -- guess what ? -- he's going to be angry at YOU. That's no way to get a guy back. There is no point in exacting revenge. Just chalk it up to experience and next time, stay away from guys who have just gotten out of a relationship and aren't ready to commit.