The Ed Sheeran scene provided some significant character development for Arya Stark.
But what “Dragonstone” lacked in action, it gained in significant character development for Arya Stark. And it was much-needed character development, after seeing her on the verge of losing her humanity during a string of brutal murders these past couple seasons. Sure, they deserved it (Meryn Trant, Walder Frey, all the Freys), but where does she draw the line now?
Pop star Ed Sheeran made a guest appearance in a scene with Arya Stark, which was a gift to actress Maisie Williams from the showrunners because she's a big fan of Sheeran. But the cameo was actually much more than just a cameo. The scene was a significant jump for Arya in her character development.
Arya just wiped out the entire Frey bloodline (save for the women), and she’s on a murderous rampage in Westeros. She's on her way to King’s Landing to murder the queen, as she tells Sheeran and his camping pals in the Riverlands. At this point, there’s no telling what Arya’s willing to do for revenge. And throughout this entire scene, there’s tension: Arya knows these boys are Lannister soldiers, and she hates Lannisters. Will she kill them, or let them go on their way?
The friendly Lannister soldiers offer Arya food, and remind her in casual conversation that in Westeros, they really have no choice but to serve their house, which just happens to be House Lannister. Not everyone who serves the Lannisters is as terrible as Cersei and Tywin. These boys are good people, and it's not their fault they're associated with the people responsible for murdering her family. This is a good thing for fans of Arya who don’t want her affinity for assassinating everyone who has wronged the Stark family to get in the way of her humanity.
From now on, it seems like Arya will let innocent bystanders go. Whether that will be good or bad for her mission to kill the queen (and the others left on her list) is up in the air. But we hope it’s a good thing, because we’re totally rooting for her and definitely, definitely don't want her to die as a result.