Do you remain friends?

For a few months I was hooking up with a guy friend who was also a coworker. No one knew not even my bestfriend/roommate/coworker. The next thing I know he has taken her to dinner and now likes her. After I break the news to her that we had been in a "relationship" she continued to hang out with him and wonders why I am not her friend. We are completely off speaking terms and awkward is an understatment, but I don't feel like we are friends.