She hugs him.
...it's actually a lot scarier, she discovers, to try to figure out what you want and ask for it and be told you can have it, than to sign yourself over unreservedly after carefully calculating how bad a decision that is and how much you care. There's an uncertainty here that wasn't here before, or wasn't relevant, when there wasn't any sense in which she was relying on him to treat her in a particular way.
But he wants—very reasonably!—her to rely on him to treat her in a particular way. (And almost certainly not just so he can betray her later for his own amusement. You would have to be some kind of flawless master of deception, to be secretly plotting something like that and yet outwardly come across as... John.)
She takes a few deep breaths, nestling into his arms.
"Okay," she says softly. "Okay. I can—" Shiver. Deep breath. More firmly, "I'll trust you." She hugs him, a little clingily. "Thank you."