@alpha1,
Look, I was married for five horrible years to a man who was jealous like your g/f. We'd go to a party and the next thing I knew, he'd be gone. I'd look for him and no one would have seen him, so I'd call home. He always came to pick me up and I'd ask him what the hell happened. He would tell me that someone (a male) was looking at me or some stupid ****. He was always sheepish and apologetic and embarrassed, but it continued for about 4 years. He left me in restaurants, house parties, parks, museums, you name it. It was downright stupid and and annoying. Then I got the bright idea to take my own car. So, the next time we were going out with others, I said I'd meet him there. He was surprised and said no. Bingo. Never happened again. He still got jealous, but he never abandoned me anywhere again.
There were many other situations where he'd get all cold on me, or bitter or whatever... it was all in his own head and he was aware of it but he couldn't stop it.
His next wife experienced the same thing. We were friendly and she'd phone and ask me if he had done this or that to me and I'd say yes, and she'd tell me how frustrated she was, etc. So he continued the jealous stuff with her. I told her to dump the bum (heh heh) but she hung in there and they're still together. They split up for a while every now and then because of this stupid stuff, but they're still together.
It's absolutely impossible to have a decent relationship with someone like that. So I understand your frustration - I just don't understand the anger.
If you realize this is HER problem, all in HER head, you might simmer down. This is NOT about you; it's about HER. And good to know this NOW, before marriage and kids.
Trust me - she'd be like this with any man. It's not about YOU at all.