Plan A:
1. Cancel the trip, and wish your friends well as they embark on a great vacation.
2. Rent a chick-flick, and buy plenty of popcorn.
3. Spend some quality time with your girlfriend as you lend her a shoulder on which to cry during the movie.
4. Go shopping with her and offer to hold her purse while she tries on the twentieth outfit that she has no intention of actually purchasing.
5. Talk to your friends on the phone. Oh, wait, they’ll be too busy having fun at Disney World to talk.
Plan B:
1. Remind your girlfriend of the circumstances involved in the planning of this trip.
2. Assure her that your relationship is secure, and that you will indeed miss her while you are gone.
3. Tell her that her jealousy concerning your joy, and her inability to allow you to have a good time if she is not involved, are not signs of good things to come within your relationship.
4. Buy plenty of sunblock on the way to the airport.
Yeah, “B” sounds better.
Basically if you choose Plan A you are saying that your girlfriend is in complete control of the relationship and that you probably won't ever get to spend time with your friends again - or only when she says gives her permission.