If you are good enough of friends to travel together, then you should be comfortable be enough to use honesty with her. She can't know how you feel until you tell her. To get all huffy with someone over an issue they are unaware of is unfair. She deserves to know your feelings.
I don't really mind extra people, but I do appreciate a "heads up" when a friend is planning to do bring some. But, for a trip, I think it's a bit rude to invite people that are "outside the circle", so to speak, without asking everyone if their cool with it, first.
That being said, I wouldn't give up my chance to have a great time with great friends because of this, because it's really out of your hands at this point. Staying home would seem like you were just being a drama queen or acting like a pouting child, IMO. It would only make you look bad.
Like I said, if it bugs you that much, stop complaining & say something to her. I get that you want advice, but, really you need to tell her what you told us, it's quite simple.
Good luck.