Her reaction, is to open her mouth only a little bit wider, only what is necessary for Natasha's tongue, and have her tongue rub up against Natasha's. Sara is more than okay with that. They don't know each other, after all, and treading lightly, curiously, is how to explore without directly asking.

Natasha doesn't seem the talkative sort.

She puts a hand over Natasha's and pushes it a little, encouraging the touch.