Tad, I am sorry you are going through this. From the brief excerpts (I hope I didn't miss much) that I resd, you didn't want this and she turned your life upside down and continues to cause you emotional discomfort.
The only thing I can imagine is that she has trouble letting you go. No matter how much our WAS complains, they typically have spent a great deal of their life with the person they walked away from. And not all the memories are bad, even though most will act as if they were living with the devil himself.
I have read more accounts of marriages falling apart and how the person that walked away ends up regretting their decision. It may happen immediately or many years down the road but almost all eventually feel they may have made a poor decision.