Game Of Thrones Season 7: 10 Ups And 3 Downs From 'Beyond The Wall'
Downs...
3. Arya's Turn On Sansa
Arya confronting Sansa about the letter made sense, as understandably there'd be some conflict there. Arguably even then Arya should be a little more forgiving, since Robb, Catelyn et al all waved the latter away as Cersei's work, but it does fit with the difficult relationship they always had. Again, there's an argument to be had about how quickly that's happened, and a lack of meaningful conversations about what each of them has been through since they were parted.
What really didn't fit, however, was their final scene of this episode, when Sansa discovers the faces in Arya's bag (and she thought Bran was the creepy sibling), and her little sister starts to threaten her life.
It's a huge leap from a confrontation about a letter to 'I'm gonna wear your face', and also paints Arya - one of the most interesting characters in all of A Song of Ice and Fire - as a somewhat cartoonish villain, like a caricature of a Faceless Man playing Arya. Maybe this is all some sort of plan to trick Littlefinger, but even if that is the case, it's not really worth the damage to these characters in the meantime.