She's just some girl whoring herself out just to get back at her x-bf. I would NEVER be with anyone who did that. She has some serious issues, no doubt in my mind after reading your post. Be single-minded about it, she's not your type right now.
Honestly, the fact that she's doing this to hurt you just means she's not over you. Don't get your hopes up, focus on your life without her in it. The best response you can have is to get over her completely and be happy. It will drive her nuts. If you do this, I'm almost positive you'll hear from her a few months from now to "see how you are" and you'll be ready to do whatever you want.
I wouldn't date much, unless you just need to see if you've "still got it." Just hang out with some good friends all the time for a while.