Once again it's the feeling she reads in him that affects her, rather than the words. The relief. And, implied by the relief, the full understanding of why she would ask.

"Good," she says, a touch more briskly than she's actually feeling. "I'm pleased to hear it. That does need to be someone's responsibility, and I'm quite certain that neither of us wants it to be mine."

(Is that a joke? Definitely. Completely a joke? ... Probably.)