I have to agree..as long as you are friends with her you have one foot in the door of his life..not to mention eventually if they keep seeing each other she will come to resent your input..
I will not be contacting the xabf ever again or even feeling sympathy. I have finally detached.
BUT not really. You are still checking up on him by talking to her. I recognise this because I have been there. I didn't "move on" until I had absolutely no contact at all whether it would be with him or with "friends"..AND it was quite a fete because we both live in a very small town. I cut ALOT of people out of my life because they felt compelled to report his every move. I wish you well.