Arya is dead. A girl is no one. This episode finally shows what Arya has become, which is to say No One. She tells Sansa, "Let's play the game of faces, I ask you a question and you tell me a lie. If i believe it, you win."
Youtube link to relevent moment in the past when A Man asks if she is No One and she lies to him.
https://youtu.be/OIz117d9CvI?t=394
>>86658866
The relevant time is at 6 minutes for this thread
>>86658866
Plot twist. Arya actually died and the waif has been wearing her face this whole time.
Meanwhile, Sansa is thoroughly triggered by "let's play a game."