NWR..Ever want to tell your coworker the truth

but can't. So my coworker asks me if I keep in touch with a girl who left working here. He's like don't you both go to the same school. You don't stay in touch? Mind you I cannnot stand this girl. She was the biggest kiss A$$ and two face you ever met. Super duper nice, always a fake smile plasterd on her face and phony to everyone, including me, and when you're back is turned would talk crap like no other. I can spot phonys from a mile away so always kept her at arms length and didn't talk to her unless I had to. I'm assuming she picked up that I didn't like her, but who knows. Of course first day of class, who do I see walk in. As usual she gave her over enthusatic hello from across the class, I'm sure she was soo happy to see me telling me how are new job is 'fantastic' Since then, we haven't said one word to one another. So I told him, actually we have a class together but we sit on opposite sides of the room. I wanted to say so bad, actually I can't stand the girl so why would I keep in touch with her?