Weel, i can tell u im in a bit of the same situation here. Met this girl who is PERFECT for me (yea, im aware of the dangers of the Oneitis, but come one, there is a point in life were u have to hold on to something...). We started dating, even she moved to my place. She founded out her ex-bf was getting hitted on by a girl, and she went jealous and got back to him. Panic is not an option, so here is my plan of action:
1.- Move on: Really, sounds counterintituive, but the whole PU arts are counterintituive. Center on something like gym/karate/collecting stams.... what ever makes you feel better and for real move on. In about 3 weeks DO NOT CALL HER or contact her in any means. If she does contact you is a positive sign, just do as Wolfwoodd says: "Hey girl! has been great to talk to you, but right now im heading to do something so i cant stay longer. See you later, have fun!". Always YOU leave the conversation, and NEVER keep conversation more than 10 minutes, this will avoid that she uses you as her emotional release, leaving you exhausted. Also you will heal and get better inside, recovering your inner game.
2.- "I had really moved on baby": Make sure that you have fun, that you go out with your friends, that you bought that nice new parfume always wanted, and specially DATE OTHERS. The fun part here is that you can date others, the cutter the better, and her friends will make sure she finds out... Also couple of "UPS! were that come from" pictures tagged on your FB profile (not by you but by a friend of yours, you dont want her to think you are bragging about it, that will lower your value) with some girls putting her arms arround you, or even kissing your chick is enough. You had become again in her eyes the fun/thrilling/mysterious guy she fell for, and together with step 1, create a fear to loose you.
3.- Contact her: You are friends, arent you? friends take a coffee or whatever together, but remember, dont do it before you see her ready, giving you IOI's, that will be about 3 weeks after the "no contact" apply, every girl is different, so u must know how to read IOI's. In that "date" (dont let her know straight is a date to get her back) go to somewhere that will alloud you both to talk and act normal. She will find again that guy who she started to date with, the guy she loves to be teased by, the guy who is very smooth and soft at hes "friendly" kino. Whatever you do, have fun with her, past is past and leave it there, no jealousy, not mentioning old problems, just fun and laughter. If you do it right, she will be back with you or really start to think about it. The rest is preatty simple
Remember, on the date have something new with you but that doesnt changes too much yourself. Like a new perfume, or an earpiercing, or just new jeans and shirt she had never seen before. You must look new, and not brag about it, if she compliments the new you just brush it off with a simple "Thank you".
Im right now on stage 1 of the plan, so far i got this: I agreed with her that the break up is for the best, and told her we can be friends. That got her REALLY pissed off, so much in 2 days moved out of my house to a friends house (or the ex, dont know, dont want to know) telling me that "the house is too little for both". Also saw same type of reaction when she founded out i got a date

I will keep the no-contact rule untill she cools down and starts to think what she is loosing. Then i KNOW for sure that she will contac me, i give her 2 weeks, wile she realizes why she left her ex in the first place (a total AFC, just got her back over jealousy and by accident, he still wondering how he did it) and that im really moving on, for real, and she is going to loose me over other girls (sooooo competitive women are...)
Hope this helps you. The good part is that if it doesnt work (most likely will) you still moved on.... NEXT!
