I just realized one more bit about the Arya story line. All of the names on her list are of “bad” people. the Insurance guy on the docks was also a bad person. The actress on the other hand was not in this category. One more possible hint that it is the Waif that is being tested?
She would have to be a complete idiot not to know that, and one thing we know about Arya is she’s not a complete idiot.
Jaquen said to her, “This is your second chance. There will not be a third.” It was clear from that what the consequences would be of failure.
Also, he knew instantly when she returned from killing Meryn Trant what she had done, even though we were not shown anyone spying on her. (And its not just being caught returning a face; Jaqen says something like “You have taken a life that was not yours to take.”) Arya may not have been aware that the Waif saw her fail her assignment, but she knows very well that the Faceless Men will find out about it almost immediately since her target is still walking around alive.