She knows that he watches her. She is not a fool, nor is she a child; neither does she, by her feigned ignorance of the matter, assume it will be resolved on its own. She knows his eyes follow her sometimes, and a secret part of her revels in the feeling of being desired, the slight sense of danger trembling inside of her when she allows herself to level a look coolly back. She knows, too, that he is neither a fool nor a child himself, despite his occasional claims to the former; she knows that he is aware of the way she reacts to him, of the way she, with her silence, implicitly allows his eyes to continue following her.
She knows, and she knows that he knows, but he says not a word of it, and in his silence she reads a tacit approval of their precariously balanced position. They are many things to each other, but there are also many things they will never be; fighting the current in this would only bring their ruination, and she senses that he understands this as well as she does. If he did not, she does not believe he would stop at watching in silence; he is the sort of man, by all accounts, who does not relinquish the things he wants easily.
Still, she knows that it is not a matter of wanting with them, but rather a matter of self-preservation. Either of them could destroy the other with nothing more than this untouched flame between them, and only by avoiding it can they avoid what would surely follow. It would be better, of course, to douse it entirely, but because he watches, and she lets him, it is clear that neither of them intends to do so; they dance around it instead with just enough grace not to tumble into the conflagration.