It sounds like you handled yourself very well in that interaction despite the fatigue -- just means you were giving off the appearance of going on with your life and staying busy, which is still attractive!
I will agree, your W's desire for small talk is weird. I keep running into that during my own sitch. We think, "You're D-ing me and running my heart into the ground, and here you are wanting to chat like old buddies?"
I think they do this to try and get a feel for what we're like without them. There is no doubt in my mind that your W, despite her chilly behavior, still wonders what life might be with you, and perhaps even misses some parts of that old life...
You're right to try not to guess what's going on in your W's head. Too much like trying to find the meaning in a Jackson Pollock painting.
