What a drama. You know, it's really up to this girl to handle her ex....not you. The issues stem from her past, not yours. If there actually IS a problem with this guy then SHE needs to take care of it (legally if possible) before she puts herself out there in the dating market. You should not have to be a rescuer for an adult female my friend.....or you will be bound to that role for the term of the relationship. Trust me, that's no fun and not healthy for you OR her. All this idiotic talk of fighting him or threatening the guy is a path you really don't want to go down. Sure, be on the alert, but is this how you want to live your life? I would let her know that if he is actually following you folks then SHE needs to handle it or you will simply take a walk. You really don't need this, do you? With all the thousands of gals out there....no matter how long you've been dating this one....I would strongly urge her to fix this nuisance (if there actually is one) or you will either move on for good or at least stop seeing each other for a while until it is resolved.