OK, everything I am about to say is coming from personal experience.
The first thing you need to is get your money back from that trip.
Quickly and quietly look for a new job. (Its a little easier because you are working to get noticed)
Find somebody....anybody to move with/room mate with.
Get the hell out of there.
Reasons why:
Once she knows that she has that control over you by threatening to turn your life upside down, SHE WON'T STOP! It will probably lead to either her snapping because you finally put your foot down. Or you snapping because you have been holding all of that frustration in, and you are by yourself. I know it sucks, been there, done that. Most people with this problem get worse and more controlling because they feel they can. I know you love her, its why you are still there but, it can only take you so far.
Women get jealous. Thats a fact but, it sounds like she acts that way because she has a problem with herself.....not you.....not the women you speak to. She will not be right until she realizes that fact. I was in a relationship for a long time and things got progressively worse, until she got violent. She might not be at that level yet but if you stay in that situation she will.
She has got you by the balls and now you have to suck it up and protect yourself.
You are still young, find yourself a young, sane girl and have fun. Just my .02.