before she left the house of Black and White; she isn't a Nobody, she's Arya Stark.

She isn't doing hits to follow the creed and order of the House of Black and White, she's doing the hits to satisfy her need of revenge at her family getting slaughtered.

Color in the lines as you see fit for her.

It'll be interesting to see if her and The Hound eventually reunite since they are both on their lonesome revenge tour at the moment.