Just tell her everything you said here. Let her know that if the situation were reversed she would be furious, and that she's not taking your feelings into consideration. Talk things out as civil as you can, yelling and screaming won't accomplish anything.
I'm the jealous type too, so I know the way you both feel right now. Just talk things out, reassure each other about every little thing, and try to get some freedom about who you hang out with as well. What she's doing would have driven me away a while ago. But if you really like this girl, just do your best to talk and get stuff figured out.
I probably repeated myself several times here, but I figured I'd respond the way I would with my voice. Hope things work out Sniper2.