FL_Ag1998 said:
If it turns out that Sansa and Arya are involved together in some sort of double cross plot and end up taking down Little finger, that'll be completely out of left field because these lazy writers have given no indication that they are working together and every indication that they aren't.
But I won't be surprised if that's what happens either, because it's obvious the writers are reading the internet comments by viewers and adjusting the script accordingly. And before any smartass thanks I'm suggesting they read texags, I'm saying that the majority of non-TA show watchers I know are also complaining about these same points.
Littlefinger might end up getting double-crossed, but I don't think Sansa and Arya are planning it together.
Sansa was caught by Arya while searching her room, and Arya explained her face-changing abilities to her.
Arya was pretty damn menacing, and Sansa was pretty freaked out by it.
If they were just putting on a show because they suspected that LF might be listening in, there's no way that they would want LF to know about Arya's training as a Faceless Man.
I think it's possible that Arya is playing Littlefinger and keeping Sansa in the dark because she has learned to not trust anyone.