Indeed.
And I don't know if they will emphasize it (it's more of a book thing) but much of Arya's training in Braavos was about lying well to people and detecting other people's lies. I think the idea is that you cannot fool a Faceless Man. So both Bran and Arya can see right through Littlefinger. Sansa may not have skills quite as developed, but she doesn't trust Littlefinger at all, so that protects her almost as well.
There was eye to eye contact with Littlefinger and Arya, and he doesn’t fool her a bit either. My bold and fearless prediction is that she’s going to kill him.