Do you have to take a parenting class in your state? If not, it would be still worth making part of the negotiating process. There are certain ground rules when it comes to children that really important to understand. It is something W probably needs to hear from someone other than you though. Then maybe incorporate some of those into the official agreement after you have both been through it.
Sorry you had to listen to the WTF logic they sometimes hit us with. She sounds like she is trying to rationalize her choice to assuage her own pain and guilt. A very normal thing to do, so even though it is hard to do, the more you can let it roll off like water off a ducks back the better for your sanity.
Still, I know how statements like that stick in my craw for days. Sending an electronic hug (we really need a hug emoticon).
Me: 50 W:43 S6, S3 M: 12 yrs. T: 17 M is bad & Not happy Bomb Mar '14 S 5 Feb '15 D Bomb 13 Apr '15 (but "no hurry") DB Coach May '15 Wants proceed on D Aug '15 Starting 1-on-1 negotiations Sept '15