LH said most of what I was going to but just to reinforce a couple of his points:
I would not recommend dialoging with her. I would suggest telling her that while you would be open to that, you don't feel it's appropriate while she's engaging in an affair. She might argue that she's not actually sleeping with him but simply talking to him is STILL an affair.
She says she doesn't feel separated and wants to. Make that wish come true. Quit ALL contact with her. Tell her to get the horse out of there. Don't do her any favors, don't let her come by, end it all. She will never learn to miss you until you can make that happen.
