"im not sure that i can be seen as a bitch and go back to her."
If you're overly worried about what others think about your decision, you don't like her THAT much.
Make sure that she really realizes that you were really angry, and what she did was in no way acceptable. If you don't make her understand that, then she could just think that she can walk all over you and then fuck you over all the time. She has to know how you felt so if she really does care for you, she wont do it again.
As for the dude she hooked up with, forget about him, it was your chick's choice to cheat, not his. Now if he did it knowingly trying to fuck with you, then it's your right to smash his head in a locker, but still, not the right way to go about things.
And besides, you're 16, she's 14, no matter what anyone says, 14 year olds aren't mature, so whatever.