Let's chart out Arya's chain of events from the last couple episodes:
- Arya quits assassin school, knowing full well that this is an offense punishable by murder.
- Arya retrieves her sword.
- Arya leaves sword in poorly lit alcove, heads back out into the crowded streets of Braavos.
- Arya books passage back to Westeros, then heads to a bridge to enjoy the Braavos view one last time. Remember, at this point, she knows the most skilled assassins in the world—ones with the ability to swap faces—are looking to kill her, and yet she thinks she has the luxury of a nice stroll at dusk. Without a weapon.
- An old lady approaches Arya; Arya reacts to her without any suspicion whatsoever; turns out the old lady is actually a faceless assassin; Arya gets stabbed in the gut multiple times, would be dead if assassin wasn't conveniently focused on torturing Arya.
- Arya heads to an actress lady's crib, tells actress lady that she wants to be the Christopher Columbus of Westeros, for some reason. Then, she drinks the Westerosi equivalent of fentanyl, despite, you know, STILL KNOWING THAT AN ASSASSIN IS STALKING HER.
This all worked out for Arya in the end—a chase scene thankfully brought her and her would-be assassin to the neighborhood in Braavos where that poorly lit alcove (and sword) was located—but man, it really should not have. For all the talk and montages—two seasons worth—of Arya becoming a trained killer, she did not play how she practiced. Arya should be dead, for so many reasons, chief among them that she was unforgivably stupid.
Ned Stark taught his children many valuable things, but he did not teach them how to think critically. In retrospect, that's probably because he didn't know how to either.
Verdict: Infuriatingly dumb (loves sunsets though!)