Which brings us to Sansa finding her sister’s bag of faces. Any question of whether the Faceless Men made Arya "magical" can be wiped away after the reveal of those rubbery faces. It’s cool to see Arya being confident and stone cold, but... she is being duped and lashes out by threatening to cut off her sister’s face. In a strange parallel to when Sansa also didn’t know what Bran meant when he said he was the "Three-Eyed Raven," Arya tells Sansa about her secret organization and their lying game, which comes off super creepy, and really hammers home that this is a little serial killer. Though we may like the people that she kills, she has a corruptible will because she’s not a true Faceless Man. She’s Arya Stark.
If you’ve ever read an argument online about if Luke Skywalker in Return of the Jedi is actually a Jedi, then you might know the difference. Like Luke in Empire Strikes Back, Arya left her place of training to deal with personal connections. Luke returned to complete his training only to find Yoda dying. Arya refused to give up her identity and serve the God of Death. We may get an answer about what happened next for Luke laer this year in The Last Jedi, but I doubt the show is going to return to the House of Black and White, so we’ll never know for sure if Arya is a complete Faceless Man. The key thing is that she's not right now, in this boiled-over state of emotion. When she’s saying what Sansa is thinking about out loud, it’s through an imperfect filter. We can trust some of it, but it’s far from accepted fact just because Arya said it. Arya is a stone-cold killer, but is still fallible, because we know she’s being tricked.