What does Dan attempt to show Diana in Act 2, Scene 4? What makes Natalie almost leave?

Back at home, Dan shows Diana several things, including their wedding rings, that she doesn't remember. Meanwhile, Natalie interjects comments about the semi-actual facts that Dan is feeding Diana, but Dan insists that things can be even better than before. When Diana is unable to remember Natalie in a photo, Natalie tries to leave, but Dan makes her stay.