If it's really "just friends" and if you two are really involved to the point of considering living together, then you should just go to the movie with her.
Flip the switch on her...
Say "Great, movies sound cool, it will be nice to meet this group" and if she pushes back on that, you can do what comes naturally.
Obviously, I'm with the rest of the majority here... I think you're getting played and she has very likely already crossed 'that line'. I don't know you, but if this relationship is seriously at the point to where you should be moving in together (which is a major mistake anyway), then this trip to the movies wouldn't be happening.
Ask yourself this... make a list of what is different with the two of you NOW compared to before her friend met this guy and his crew? Hell, put on a hat and glasses and go to the movie - have a friend go and check out what happens with that group. It will clear things up a hell of a lot faster for you. But, if it is just friends and you're busted ... then yeah, you're SOL. So, have a buddy go.
I can understand her having guy friends... with people she knew before you two were an item, but this li'l episode won't end well.