Yes I agree with RP (as I usually do) about thinking about what you want to get out of this relationship and what your needs are. Labels are fine but they often mean different things to different people. She may have so far had "friends with benefits" because she hasn't understood any other options to monogamy.
For your relationship to have any chance to work on a level beyond "friends with Benefits" you are going to have to learn how to communicate with her really well. If she isn't up for that kind of work you are going to have to decide whether you can work with what she wants.
Jealousy sucks, but again, dealing with it works best together. If she won't come to the party well...that's a whole other story and I don't know if there is much around about that here. There is a really lovely video on the blog Hot Poly Mess
, about being alone.
Keep us posted. I will be interested in how you go. I have a post on my blog (link below) on jealousy but it really applies to committed relationships. I'm sure you aren't turning into a pyscho and plotting to do terrible things to her car.
At least I hope not.