What was the point of the last scene between Arya & Sansa. Arya is all taunting & threatening Sansa, then goes and give her the dagger... for what reason? To give her a fair chance if her sister goes after her?
I hope it's for her to take out Littlefinger. It's his dagger. From Arya's perspective there are only two possibilities: Sansa is a traitor or Littlefinger is behind this. She threatened her and played the game of faces to see if she was honest. The faces are a threat, but it can also be saying "I can be littlefinger, you don't need him anymore". Or nothing of this happens and Arya is stupid.