Most Helpful Girl
I would take things slow. I wouldn't break up with her.
As a girl I can say that I have done something similar to your girl and it wasn't a case of being a Jezebel I just had to find my own answers.
Just be careful and take things a little slower from here for a while to hopefully you gain some more trust for her as I'm sure this incident has left you wondering whether you can trust her again or not.
If she doesn't seem loose in generally then I would believe her confession and apology are genuine. :)1THIS IS NOT RELEVANT ANYMORE