I agree with the above posters, but I'll add a bit of zest to it...

If my long time girlfriend/fiance, was emotionally cheating on me, and doing things like going out on a date with a coworker, I would not hesitate to seriously ***** her out. That being the polite way of putting, even. I would not tolerate that kind of shit. I can tell you that if the same thing happened to me, I would tell her to chose... either be completely honest with me and start fessing up to how sorry she is, and how disrespectful what she did is, or.... have her ass hit the road.