She at least knew him well enough already to know that this would elicit a reaction from him. And then she went and sought exactly what she wanted. Like moth to a flame, he went where he was pulled and he was reaching for her, as he did that night.
Yelena hasn't thought too deeply about her attraction to Will Graham. Not beyond the obvious, at least. As Natasha pointed out, and she pointedly ignored, he was cute. In that floppy-haired nerdy stuffy professor way. Except he definitely wasn't being nerdy or awkward right now. And she really did like the stuffy professor look. Buttoned up on the outside, something else dark and far more interesting lurking just beneath the surface.
Will said he was used to people using him. Was this yet another way for someone to use him? Another strange coping mechanism of sorts? Only that she was strangely comforted by him in a way that no one has matched before. So, if Yelena could be seen as also using him, her reasons weren't so hidden.
"Oh really?" He was keeping some distance, holding back, but Yelena arched towards him as her hands gripped either side of his hips. "Teach me."