And so her old "friend" is back... what now?

To cut a long and aggravating story short, my current relationship has survived a proper relationship killer. My girlfriend had this gay friend, they took their friendship a bit too far. Her way of thinking was something along the lines of "its ok if he's gay", and his love for suggests he's not entirely gay. Not going into much more detail here, but he's been gone now for a long time, we managed to cast that dark shadow out and I managed to come to terms with all the creepy **** I've seen. But now, starting june, her boss employed him and now they'll be working together. I can't have them anywhere near each other. What do I do?