Yeah, I'd have to say if she could cheat on you after being away from you for just 3 days at math camp, then there's a very good chance she'll do it when she's off to college, she's gonna be living on her own and doing a lot of partying, and once a cheat, always a cheat. You'll be better off just making a complete break from her, and I'm sure you wont have any trouble finding someone else.
I'm not sure if she was, but your first love is always the hardest to get over.