Maybe she is confused about her choices, and after she opens up to you and is warm and pleasant, she realizes what she did, pulls back, and sends another d email to let you know there's still a wall there.
Maybe this is how she's re-setting the distance?
After my first ex walked out on me and his daughter, so he could start his new life, he would contact me in a similar fashion as your w contacts you. He would also come by late at night for these "can we just talk?" episodes. Or there were emails and voice mails. I allowed this to go on because some small part of me had hope inside that the reason he was contacting me meant that he was going to come back to me. I held on to it for a long time until I woke up and realized that for every time he contacted me, a nasty period would follow. I was just putting up with the nasty stuff too long and finally shut him down. Finally got my nerve to just tell him not to contact me unless it's about our daughter. He reacted like a child and threatened to take the car away that we agreed was going to be mine.
After a long time of the back and forth I got tired and decided enough was enough, either he's coming back or I'm moving on.
With my H, it was different. He did not really want to leave (as he revealed in MC), so when I detached, it scared him.
I think you are doing a good job WHG at balancing all of this. I hope I did not come off as detachment as being easy because it is not. It's the hardest thing ever, especially with kids involved. It's so hard to know what to do in each situation that comes up. I have found myself sitting alone thinking.... if I do this, what will happen. If I do that... then what! It's very stressful.
Do some good things for you WHG. Don't forget to take care of you, and do special things for you too.