You know my sitch and you know who I was when I was lost and who I am now. There wasn't a thing in the world that my H said, no matter how true it was, that I heard THEN. But when I came around after 2 years every single word he said to me was right back, echoing in my ear. So if you do it tactfully, it could help IN THE END, to say what you feel. However, you know she'll be pissed but remember...the more true the words are the madder the WAW is going to get. But it's good, it keeps the "running" from going on endlessly and make no mistake, she is running. Every bit of truth you can hit her with - respectfully - aids in bringing her around the mountain. I've been there. I know. My H and I lived together, too for 15 months with my heels firmly dug in and I wasn't budging. We DID have good times, like you all do. But they were not long lasting. When I opened my eyes to reality though, I remembered those times and they mattered a lot to me.
Your W should be more sensitive to D's feelings. It is very disturbing that she disregards them and re-emphasizes that nothing is going to change - D is immenant. That is sad, that she disrespects them so much. That's a life altering mistake on her part that they will pay for. Very unfair and I can not say I understand that aspect of her current mentality.