Let’s look at one of the prominent Arya theories that has been floated out there. Even though it appears that Arya did in fact kill another person called the Waif, some theorists are still hanging onto the notion that Arya had to either kill a part of herelf or die to herself to fulfill her fate in Braavos. Maybe part of that dying involved stabbing herself? Okay. Lady Crane didn’t attend to fake wounds.
Did a piece of Arya actually die? As part of the process of becoming No One and then Someone, it’s plausible. She’s learned how to outwit the Waif and even Jaqen himself. Chances are, Jaqen was hoping Arya would make the choice she did. Her certainly gives us a hint with that little smile after Arya declares herself as Arya Stark and that’s she’s going home.
An Arya Stark future puts a former disciple of the Many-Faced God directly in the midst of other characters and their goals. Arya Stark of Winterfell is probably going to derail a lot of plots and schemes before the tale is told.