It was a complex relationship for sure, but I also don't think the HBO writers made it an inconsistent relationship (as was argued previously). I could fully believe that Arya would clean The Hounds neck wound and also abandon him to his own devices when pushed too far.
I guess I just didn't
see the conflict that Maise talked about. In a book, it would be more obvious why she walked away, because her thoughts, mental state, emotions are literally explained for you. In the show, you just see her blank stare as he is writhing in agony. this guy who she actually likes and who she looks up to.
in her interview, she explains that she walked away because him ordering her to kill him was the "final straw" that made her choose to walk away instead of putting him out of his misery. I guess I just didn't see this in that scene.