Visual reminders point to this and Game of Thrones costume designer Michele Clapton makes note of this in a behind the scenes post saying "Sansa's cape, for instance, represents Ned and her desire to take on more of a leadership role at Winterfell". The Starks also represent ice, and with Jon's strongly suggested lineage from both the Targaryen and Stark lines, he would represent the combined fire and ice ... the lynchpin of the whole thing.
Despite the fact that she has learned to become an expert killer that's cold and remorseless, one thing is worth remembering.
The episode works to set up the season finale as well as the final season of Thrones: The White Walkers are almost at the Wall now, while Daenarys, Jon Snow and the others are on the other side of the Wall, preparing for a meeting/peace conference with the Lannisters. But some fans aren't willing to accept that all is lost.
Renewed interest in the theory seems to have started with Reddit user turm0il26 (though with so many fans sharing so many theories it's hard to know exactly where some come from), whose argument boils down to the idea that Bran has been continuously going back in time to try and save mankind from the White Walkers, with each attempt failing, and his efforts eventually ending with him getting stuck inside the Night King. Specifically, why she, an expertly trained assassin, allowed herself to be duped by Littlefinger and then threatened to cut her sister's face off over an insignificant letter written six seasons ago. GoT is a wild show, so it's possible something violent that doesn't end in death could happen to Arya and Sansa next week. We admit that imagining a reanimated Arya with ice blue eyes does not really reassure us and we hope that it will not happen. Sansa needs that army and the only way to get it is through marriage. Sansa saw a connection between Brienne and Arya, who have been training together since Arya's return, and it could be in Sansa's best interest to send her away. The Lady of Winterfell made a decision to send Brienne away to King's Landing.
Arya and Sansa's conversation in this scene goes beyond the typical, "What are you doing in my room, dear sis?"
For plot reasons, it's clearly important to establish a rupture in this relationship and establish it quickly - Arya's discovery of Sansa's alleged betrayal of their father has helped facilitate this. Is this what will finally force Sansa to take the North from Jon?
The theory focuses on Arya, but there's plenty about Sansa too. This weeks Game of Thrones episode, "Beyond the Wall", went a step further in cementing the feud between the two siblings, having Arya confront Sansa about the letter she wrote earlier in the series and seemingly testing her abilities as a ruler. If Sansa can gain control of that army and kill the master manipulator of the ladder of chaos himself, that will prove she is a true player in the Game of Thrones. That's just one example of a larger pattern on the show of characters not being able to see the bigger picture, only fighting the battles immediately in front of them. She wants to bump off everyone on her kill list and then ...?
A terrified Sansa did some snooping of her own and discovered Arya's "faces".
But that's not what we're here to talk about. These noises are very deliberate. What doesn't make sense, however, is to blame Arya and Sansa for their inability to communicate and work with one another.
However, the Three-Eyed Raven - that omniscient killjoy - promptly warned Bran that "the past is already written" and "the ink is dry". "The world doesn't just let girls decide what they're going to be", Arya tells her sister. Neither of us got to be the other person, did we?