I am part of a delegation to an international summer camp. How do i deal with someone in my group I dont like?

Only you can run your mouth so take control of that. You cannot control her, she is into pushing peoples buttons and she has found yours but the game doesn't work if you don't bite when she dangles the bait. Stay cool, keep clear of her as much as you can, The calmer and more mature you are when she goes off the more like a nasty B she is going to look to anyone who is watching. It is good that the adult recognizes her for the problem she is and you can know that they will support you if it comes to a confrontation. Don't let her get you down. She can only spoil things if you let her tell you how to feel and be.