Gallop30 said it best. Do nothing. Do not contact her, avoid her calls, no txts, NC all the way. I would block her from my cell. You can use googlevoice for that. It sounds like you are almost over her and you really don't need this right now in your life.
SnippotII also has great advice. Where was she when you needed help and were dealing with the shock and pain of the breakup. Let her deal with her own demons, guilt or other emotions she's feeling right now. Talking or seeing her will only set you back. The only reason she showed up was for her own selfish reason. She feels lonely, she feels guilty, she needs emotional support. Sorry to be so foul, but f that. You gotta be strong and just walk away. It looks like your having fun with these new girls. Good for you man, you really don't need to be dealing with your ex's demons right now. Walk away and be strong.