Ex-gf and i sat opposite each other, in the office everyday and it was just a dreadful experience. Her approach was avoidance, where she would go out of her way to totally ignore me and won't even say hello. My way was denial (fake it to make it kinda thing) by putting up a front to everyone that nothing was wrong. It became apparent, after a few days that this made things worst, because the office atmosphere got awkward. People didn't know what to say around us, let alone pick sides.
In the end, i confronted her and we both agreed to be as professional as possible because it was beginning to affect other people. We said our hello etc. but kept conversations strictly work related and to a minimum. We acted like business associates. It made things a tad smoother because we knew the boundaries, but it still sucked. In a strange way, I'm kinda glad it only lasted a month because i was laid off on the same day as the breakup. Lesson learned: never get in a relationship with a co-worker that you'll see everyday.
My advise: If you two can't be mature and professional, talk it through and lay down some simple ground rules. Otherwise, one of you
will misinterpret something said or done and get more confused...and even angry (as if the breakup wasn't bad enough); trust me, your emotions will be all over the place.