Hmmmmmmm it's an interesting, albeit painful quandary you guys have.
In 34 years of marriage, you can bet I thought of walking away many times, but the con side of the ledger always outweighed the pro column.
When women decide to leave a marriage they've already put a lot of thought into it and feel like they've worked hard to keep the marriage together but for some reason (and usually that has to do with the H)it's just not working. We like security, we have a need to make sure our children are safe. So they work out what will happen with the kids, who will get the house, furniture, soup tureen, how the money will work out. It may all be pie in the sky but she feels somewhat secure in her decision.
This means they are in a very different place mentally.
Spartan, it sounds like your W was processing things that were upsetting to her. You were there, so you got to hear it all. I'm not sure listening and validating her world view is the best option at this point.
Putting myself in your W's head, she's trying to convince herself and you, that her decision is a good one. What if you had said: "Your friend brings up some interesting points. Has she been through a D?" or "W, I agree with friend. I think this is going to be very hurtful for D." or "W, I don't agree with you on this so perhaps it's better that we don't discuss it" and go to another room.
You aren't resisting, you aren't arguing, you aren't coercing, you're simply stating a deeply held belief.
Is that going to make her wake up and smell the coffee? Probably not but at least it doesn't turn you into girlfriend/confidante.
Don't give up your fundamental beliefs to DB.
Me 57/H 58 M36 S 2.5yrs R 12/13
Let me give up the need to know why things happen as they do. I will never know and constant wondering is constant suffering. Caroline Myss