Hi Bill Yeah, I have to agree, she does sound sort of delusional.
And when my H was in the midst of his delusion, the one where this 24 year old co-worker was going to be with him, he would act the same way your wife is. He would say the dumbest crap...."I hope you meet someone who can take care of you so I won't have to worry about it." Seriously. I laughed. And what's worse is during this time, his stupid OW was so afraid of me she would call, text and email me that she had absolutely NO intention of being a step mom. (Unfortunately, she was not telling him that during that three week period in late December early January. But mid January, she posts on FB about her new younger and much richer boyfriend....H was singing a new tune after that.) Any-hoo.
Yes, I did start then to make it very clear, D was not going to be friendly and we weren't going to be Bruce and Demi like he seemed to have delusions of granduer over. I made it clear to him, we would co-parent and it was all or nothing with me and him. Married or people who had a child to raise together.
I don't think he believed me then. I'm pretty sure he does now.
You do need to give her a clear picture of what D would be like if she's seemingly delusional about it now.