The more I think about that scene the more I think it was her playing him playing her. The obvious "hiding spot" she was standing in was basically in his direct peripheral, she didn't look very well after he had left his room. I feel as a faceless man (basically) she would be able to be a lot more discrete if she wanted to be. It was almost as if she wanted to see what LF would feed her, as a way to see what type of game he is trying to play with her/the Starks. Maybe that is just my wishful thinking, though, as I thought I saw them arguing in the preview for next week.
She wants to know what he wants her to think. Then he thinks she has the upper hand while she turns Sansa against him by telling her that he's planting this stuff and then she can kill him.