I'm thinking more and more how Ayria got to the Night King....and I wonder...is it possible for her to have taken on the form of one of his generals? Can she take the face of an undead?
I doubt that happened. The white walkers were right behind the Night King the entire time once they entered Winterfell. I don't see how Arya could have killed one of them and taken their face without being noticed.
“Whoever fights monsters should see to it that in the process he does not become a monster. And if you gaze long enough into an abyss, the abyss will gaze back into you.”