Natasha grinned, a ridiculously fond grin because he was so stupidly charming, especially with that added little burst of indignation. It made her want to tease him in that same fond way, to let him know she'd liked that he'd asked, that she appreciated it - she loved it so much that they kept laughing through this, it was rapidly becoming her favorite thing about it. How much delight they were both taking in each other, in the act itself.
She opened her mouth, right on the verge of some silly, teasing response - and then he drove the words out of her brain altogether with the work of his hands. Obvious, yes, that was one word for it, they both knew where this had been heading, this was the point. It should not have been a surprise to be touched like this, it was so - small, it was just leadup, wasn't it, just foreplay and fairly straightforward. Still. It was enough to shut her up, entirely, enough to make her hips pitch up and it was - God, one touch and it was so clear how much she got from it.
The noise she made when he dragged his thumb was something guttural and wordless and so embarrassing that she let go of his hair to cover her face with both hands, a move that got her laughing, again, mostly at herself, her own reaction, before she lowered them again to look at him, openly delighted, a little bit amazed. "I'm pretty into this, in case it wasn't - patently obvious that you're doing great," she said, slightly breathless, lowering her hands back into his hair, the way he'd requested.