As per this Arya / Hound dialogue , Arya tells the Hound her kill list:
- Walder Frey
- Meryn Trant
- Tywin Lannister
- Melisandre
- Beric Dondarrion
- Thoros of Myr
- Ilyn Payne
- Gregor Clegane
- The Hound
- Cersei Lannister
- Joffrey Baratheon
As per this Arya / Waif dialogue at 2:10 Arya only says:
- Cersei Lannister
- Gregor Clegane
- Walder Frey
waif: "That is a short list. That can't be everyone you want to kill. Are you sure you are not forgetting someone?"
Arya: "Which name would you like a girl to speak?"
Did Arya actually fail this test? Did the waif know Arya was lying about the length of her list and then started testing her by using the second person pronoun, you. And Arya did respond to you. Previously, Arya only talked about herself in the third person.
Or, had Arya's feelings actually changed? Realizing she was too blood thirsty, she had shortened her kill list even before going to Braavos?
And, what did Gregor Clegane ever do to House Stark? Why is he on the shortened kill list? Tywin did order him to raid the Riverlands in season 1, and House Tully is from the Riverlands, and Arya's mother is from House Tully... so is that why Arya hates the Mountain more than even Joffrey? Tywin? (Arya could not know that they are both dead
)
Addendum
Unlike her killing of Meryn Trant, I bet Arya now has "permission" to assassinate Cersei, the Mountain, and Walter Frey. After all, she was not whacked for saying those 3 are on the kill list.