It sounds like a fling to me and here’s the reason why: She was very, very hurt by what she thought you did and in order to feel safe again, she replaced you with someone who is your opposite. By choosing someone who is your opposite, she rationalized that he would never hurt her in the way that you did (or what she thought you did) because he is so different. That the relationship appears to be moving very quickly is another sign that she’s trying to get back what she had with you from this other guy — a long term relationship.
So, yes, I think it’s a fling — however, that doesn’t mean that the two of you aren’t over. 😳 Giving her too much space after your blow up where you were both reactive, may not have done what you figured it would. Your break up was based on a miscommunication and it sounds like she also misconstrued your giving her space as not caring and moving on, yourself.
My suggestion is that you write her a letter explaining your feelings and that you’d like to see her again. You’re going to have to win her back — it won’t be as easy as walking into a room and claiming what’s yours since she’s dating someone else now.
I hope that helps. Let me know how things go, and I hope you’ll follow me @AskAprilcom (no dot!) on Twitter and on Facebook at this link: [url][/url].