Read a very plausible theory that Arya (and possibly Sansa) are totally playing Littlefinger right now, taking advantage of the fact that he doesn't know she's a faceless man/ capable of changing her appearance. Think about it: if Arya has a bag of faces to change her appearance, why be so completely obvious about sneaking into his room with her own face to search? Also don't forget that she has extremely heightened senses from her time being blind during her training. Does anyone think it's possible that she knew he was watching while sneaking around? Also, she told Sansa they were playing a game where lying effectively was the objective, thus all the threatening talk of what she might do (aha!) Very interesting to think about.