She already does so much more than they'd ever ask for! Even if they would very likely not ask much of anything in the first place, but gosh!!

"Hmmm, we could give you a little more room, if that's what you want," he suggests, playing along as if the inches she had on her side of the bed weren't any good. Absolutely ridiculous, both of you, jeez. "More space for our good, hardworking friend who makes sure we're well taken care of."