The power of detachment...
Very good explanation on the narc thing, Open Eyes.
I've been researching covert narcissist, and even more specifically covert passive aggressive narcissists. It's mind boggling. They can go so far as to pretend to have brain damage just to stay in control. Hard for neurotypical people to even begin to wrap their heads around. Even worse if you're an empathic person.
When he senses that he loses his power and control-over, DH goes into what I call "good boy mode." He's suddenly trying so hard to be nice and cooperative, but it's probably just childish fear driving him to try and reel us back into a place where he feels he has more control. It's likely just an act, not a change of heart.
As Open Eyes indicated, they are master manipulators, and masters at playing the victim, so watch out. When she comes up against your detachment and strong boundaries, she may switch to the victim card, and even involve others. Don't expect her to stay in a rational place. Stay strong...