Ghost, I think the only thing to do here is weigh your options. If she's hot, cool, funny, and a stoner maybe you could put up with her possessiveness. But if you think her being possessive is just too much for you to handle, then maybe you should just stay friends.

Btw, by taking your relationship further you may be able to calm her fears and she'll let up on you a little bit. Or she'll turn into a complete psychopath, either way, it's a wait and see kind of thing.

It also depends on how horny you are.