I love how kat says it. Treat her like you would the mailman. Common courtesy, but nothing beyond that.
I will tell you, I treated XH the same way you have been treating your XW. It's that old analogy (and I think Andy Stanley uses it in his message on Anger (brilliant one by the way)) He says that anger and bitterness is like you drinking the poison and waiting for the other person to die. Your anger with her for breaking up your family is eating at you more than it is her.
I found that I had to take a step toward my XH in order to give up that anger I was holding. I actually apologized to him for treating him like he was a pariah. I did admit to him that talking to him and seeing him more than absolutely necessary was painful to me and I was avoiding that as much as possible but I realized it was coming off like I was just being nothing other than a royal b!tch. He smiled at that, thanked me, and we moved forward with a lot better communication after that.
Do you feel it may help you to smooth over a few things by letting her know that your avoidance wasn't so much about her as it was about your own pain?
T19 M15 S19 XH47 M43 bomb12/4/07 PA5/07 S12/26/07 D final 11/17/08 Back together with no defined R 05/2010 confused....to say the least!!!