This is tough I can imagine. DO NOT give up HOPE ever. There have been numerous M's reconciled even after the BIG D is final. I think her reason for wanting it quickly is to avoid the emotional ties with you. The longer it takes the more time for her to have a change of heart and right now she is so lost and confused she doesn't want to think of that possibility. Just my opinion though.
Do what you can for D and remember to be a friend for W, regardless of how this ends you and she will always be bonded since you have a child together...one day you will be marrying her off together and then grandparenting together so a divorce is simply the end to a piece of paper not the bond the two of you will forever have.
Odd question here...could you or would you contact her ex-H and confide in him or is that totally out of the question?
Both 35 T 19/M 15 years S8/D5 It's over bomb/ILYBNILWY 12-22-07
