It's been a long time coming (almost five whole seasons to be exact), but Arya and Sansa reunited on Game of Thrones Sunday night, and the one thing that's painfully clear is how much both Stark sisters have changed. Arya is now a hardened and trained killer, and Sansa cares very little about falling in love and marrying into royalty now. As they got reaquainted at Winterfell and Sansa watched Arya step in to train with Brienne, it showed her how much her younger sister had changed over the years when they were apart. What Sansa thinks of that change, however, has yet to be determined.
When Arya showed up at Winterfell, the guards tried to turn her away. She managed to get into her rightful home anyway because she's Arya Stark of Winterfell, and she can do pretty much anything. But when Sansa and Arya reunited in the crypts, at Ned's statue, it was the perfect moment. Well, as perfect as it can be, returning home after your parents have been slaughtered and you barely know the rest of your family anymore.
Honestly, Sansa is in a weird position right now. She's in charge of the North, but also trying very hard to stay two steps ahead of Littlefinger. Arya has finally come home, but she's obviously a trained assassin who can't leave that life behind her. Bran is very much not Bran anymore.
Even so, when Brienne watched Sansa and Arya wheel Bran into the courtyard together, she was all of us, looking at the Starks reunited finally. The last time Arya and Sansa were together on Game of Thrones, it was back in Season 1 when Ned was about to be executed at Joffrey's command.
Since then, the two have led very different lives. Sansa was basically pawned off on awful man after awful man, and Arya just barely escaped death multiple times. Their reunion on Game of Thrones wasn't strained or awkward, but it definitely made the differences in their experiences over the past few seasons that much more apparent.
The one thing that will forever link Sansa and Arya, though, is their hatred for the Lannister family and their shared desire for revenge, even if they have different ways of going about getting said revenge. In other circumstances, Sansa might express concern over the person Arya's become. But with the White Walkers undoubtedly coming soon, and literally everything else going on right now, Arya the trained killer is what they're all going to need.