Judging by her response it doesn't seem to phase her too much.

Personally, I'd cut her loose and call it a day.

What you should do now is use it to your advantage. Don't over do your good-bye. Be a gentleman about it and just basically tell her, preferably within ear shot of all her available single and good looking friends, that she simply hurt your feelings and treated you badly and you're simply not going to take that.....have a happy life.....and see ya.

I promise you that you will reap much more "rewards" that way. It's over between you and her, as well it should be IMO. So don't waste this opportunity to use it to your favor. She didn't hesitate to step on you. Now, take that situation to get to your next level.

Girls like to see assertive and stand-up kind of guys. You can kill two with one stone if you play your cards right.