dude...really? You haven't learned shit. Forget about her. Have you broken up with her yet? If not, why the fuck not? You don't even need a reason or anything. Just tell her you think it's time to move on and I doubt she will say much but, "OK, I agree."
You're just going to look like a complete tool if you go around showing up at parties where she is at and you weren't invited to. Then you'll get into a fight over this bitch with some guy who doesn't know or care about you? You're an idiot.
Just fucking dump her and move on already. How much more of your time do you want to waste on her? She's already sucked how many years out of you? And you want this to keep going?
Do me a favor...take an open hand, held out to your side and as hard and fast as you can bring it up and slap the fuck out of your face. That's from me, bro. Because I care.