Like Steve said, many of us know how you feel. my x is the same with the niceness. I sometimes wonder if it isn't them starting to realize that the grass isn't necessarily greener, that we shared some things that will be missed.
And that's probably the case to a certain extent. She feels guilty, misses some stuff, but ultimately has moved on and wants you to do the same. In my case, I think my X thought we could D and "be friends", which would make everything okay. She's now starting to realize it doesn't work that way, that she gave up certain things. Missing those things doesn't mean she wants to come back, but it does mean she keeps tugging my sleeve hoping to recapture a little of what she once turned to me for. I've chosen to respond in a friendly manner, but not as a friend.
Hope that helps - I know it's hard. But women like confident and self-aware men, not men who pander and compromise themselves, or men who need someone else in order to live.
