When Arya Stark (Maisie Williams) at long last returned to Winterfell to find that the rumors were true and her family had reclaimed their ancestral home and eradicated the evil Boltons, we were overjoyed. Arya reunited with Sansa (Sophie Turner) and Bran (Isaac Hempstead-Wright), who had also recently returned home to Winterfell. At long last, for the first time since the first episode of season 1, the three living Stark children were reunited and shared a scene together. However, this being Game of Thrones, the Stark reunion scene was awkward - and the joys were short-lived.One would think each Stark would breathlessly share tales of how they each found themselves back in Winterfell, commiserate on their terrible experiences and what horrors they each overcame, and resolve to never be torn apart again. However, as previously stated, this is Game of Thrones. Conversations one would expect siblings to have never materialize. Instead, Bran, the Three-Eyed Raven, is largely uncommunicative and growing more inhuman with each passing day, Sansa chooses to preoccupy herself with the daily affairs of running the North as the Lady of Winterfell, and Arya... is dangerous. Whether she's flaunting her fighting skills with Brienne of Tarth (Gwendoline Christie) or engaging in the most predictable cat and mouse game of snooping with Littlefinger (Aiden Gillen), Arya quickly displayed that she has no place in normal society. Arya makes no effort to hide what she has become: she's a killer, and proud of it.In "Beyond the Wall," after having been manipulated by Littlefinger into finding the note a much younger, much more frightened and vulnerable Sansa was forced by the Lannisters to write, Arya assigned Sansa blame for her role in their father Ned's execution. That Sansa wrote the note, pledging her "love for Joffrey" and urging Robb (Richard Madden) to come to Winterfell and bend the knee, under duress didn't matter to Arya. She holds no curiosity to what happened to Sansa and how Sansa survived the six seasons they were apart.Arya's memories of Sansa are of her callow and selfish older sister who wanted to be a Queen at any cost. Sansa's lies in defense of Joffrey forced Arya to abandon her direwolf Nymeria to the wild; that Sansa suffered her own direwolf Lady's execution in Nymeria's place doesn't give Arya any guilt. Arya remembers how Sansa stood a few feet away as Ser Illyn Payne chopped off their father's head. (Never mind that Sansa was helpless to do anything and was equally horrified to witness it, if not moreso.) That Sansa was held prisoner for years by the Lannisters means nothing to the Arya; her sister deserved it, because she's selfish and weak, and in Arya's mind, Sansa always will be. But the hard truth is Arya is more like Sansa than she thinks; in fact, at this point, while Sansa has grown into a responsible political leader skillfully looking out for the well-being of her people, Arya has become more myopic and self-absorbed than Sansa was at her childish worst. Sansa grew up, Arya grew twisted.Did Arya add Sansa to her mental List of people she will kill? It seems that way. "Beyond the Wall" concluded with Sansa finding Arya's bag of stolen faces from the Faceless Men of Braavos and Arya threatening her sister with bodily harm. Arya is unhinged and is now a genuine threat - a trained murderer in the fold with the means and ambitions to do something terrible she hasn't yet disclosed. However, by threatening Sansa and letting their childhood feud overshadow the reality of the women they both became, Arya is pointing her killing blade at the wrong person.Fans have always loved Arya since Game of Thrones' beginnings, and throughout everything she has endured, her journey has always been seen as a heroic one. Spending most of the past few seasons isolated from the rest of the cast and ultimately finding her way to Braavos at the invitation of Jaqen H'ghar (Tom Wlaschiha) to become a Faceless Man - an identity-stealing assassin - we hoped that despite the abuse she suffered at the hands of the Waif (Faye Marsay), Arya would acquire the skills she would need to become the avenging angel for the Stark family. Arya sought the means to be able to kill the enemies of the Starks, and once she left Braavos, she did just that by avenging The Red Wedding and murdering Walder Frey (David Bradley) and his male heirs. Arya's next stop was King's Landing before Hot Pie (Ben Hawkey) informed her that it was safe to go home to Winterfell. However, though Arya has changed for the better in her skillset, she was worsened mentally and emotionally: the new Arya, a professed serial killer, only sees targets - names to be scratched off a list.

Littlefinger and Sansa Stark talking at Winterfell on Game of Thrones

Before threatening Sansa with her 'discovery' (manipulated by Littlefinger) of her letter to Robb, Arya shared memories of their father, who always supported Arya being different from other girls. Arya learned a lesson the day she outperformed her brothers at archery: "The rules are wrong." Arya was always going to defy the expectations of what a Lady Stark would be. Does Arya ever ask herself if her father would be proud of her for the murders she committed, for becoming a serial killer? Even if he were, Ned (Sean Bean) would never want Arya to choose her own sister as a target, no matter Sansa's perceived crimes against the Stark family. Indeed, Arya's life choices essentially make her an outcast, not just from Winterfell, but from most of civilized Westeros. She can never have what passes for a 'normal' life in Game of Thrones. Nor does she seem to want one. Her life options are now limited to murdering her enemies until there's no one left to murder. Then what? What kind of future can Arya Stark have?

It's rather fascinating how perception of the Stark children has changed. When the series began, Sansa was generally loathed while Arya was the Stark fans loved the most. Meanwhile, Bran elicited everyone's sympathy after being crippled from being shoved out of a window by Jaime Lannister (Nikolaj Coster-Waldau). In the years since, Sansa has survived abuse, torture and rape and emerged stronger and more heroic for it. Bran became less and less of a person as he grew into his power as the Three-Eyed Raven. Arya remained someone admirable in spite of being a serial killer because she was a true survivor and she was taking revenge on the worst people in Westeros. But now Arya is threatening her own family.

It's entirely possible all of Arya's lurkings and sinister threats amount to an elaborate mind game and that her true target isn't Sansa at all - it's Littlefinger. Indeed, while Littlefinger is busy pulling the strings behind Sansa's back and actively working to pit sister against sister - he engineered Arya discovering Sansa's letter - Arya could be onto him the entire time. For all we know, Arya has been wearing the faces of various people in Winterfell Littlefinger has been speaking to, and her threatening Sansa is all part of that ruse. Even if that turns out to be the case - and it's very possible Littlefinger's demise is Arya's season 7 endgame - there's a certain cruelty to the way Arya is engaging Sansa. The enmity between them from when they were children has never gone away, and forgiveness is not a trait her short, brutal life has taught Arya. No matter how this ends, it's hard to see how Arya could be allowed to remain in Winterfell; the North and its castle will always be her home, but she has no place in it.

Game of Thrones' breakneck-to-a-fault speed in season 7 has been jarring, and Arya's sudden descent into murderous madness is a result of that. But a madness within Arya was always there. The series asks the viewer to decide for themselves whether all the deaths Arya has been responsible for still allow her to be considered a good person. Most of our beloved characters are killers after all, and how much we like them doesn't necessarily depend on who they've harmed - look at how fans have warmed to Jaime despite all the terrible things he's done. As long as Arya kills people we hate, she'll remain beloved, even as she grows more and more disturbing. But if Arya kills Sansa, then she will be the one who betrayed her father and everything the Stark family stood for. Killing her sister is the line that, once crossed, will leave Arya Stark beyond hope of redemption.

NEXT: WHY DAENERYS WON'T BECOME THE MAD QUEEN

Game of Thrones season 7 concludes Sunday, August 27th @ 9pm Eastern on HBO, HBO GO, and HBO NOW.