I just want to take a little time and appreciate this quote by Arya:
Thereafter she and the waif spent their time together touching things and pointing, as each tried to teach the other a few words of her own tongue. Simple words at first, cup and candle and shoe; the harder words; then sentences. Once Syrio Forel used to make Arya stand on one leg until she was trembling. Later he sent her chasing after cats. She had danced the water dance on the limbs of trees, a stick sword in her hand. Those things had all been hard, but this was harder.
Even sewing was more fun than tongues, she told herself, after a night when she had forgotten half the words she thought she knew, and pronounced the other half so badly that the waif had laughed at her. My sentences are as crooked as my stitches used to be. If the girl had not been so small and starved, Arya would have smashed her stupid face. Instead she gnawed her lip. Too stupid to learn and too stupid to give up. - Arya II AFFC
Here we see Arya’s perseverance and it’s so admirable. She is comparing the difficulty to learning languages with sewing (and we know sewing is incredibly difficult for her, most likely because she’s left handed) and we see in the books that she accomplishes this difficult task of languages. In TWOW, we see Arya, playing the role of Mercy who is a native Braavosi, who doesn’t even know the common tongue, meaning Arya was completely fluent by this time. So we see Arya really struggling to learn Braavosi to someone who is completely fluent in the language in a span of probably 6 to 9 months. That is incredible! And not only does she know the common tongue and Braavosi, but she’s brushing up her High Valyrian - it’s likely she’s already completely brushed up on it by the time Mercy takes place - and she’s also learning the tongues of Lys and Pentos too.
A lot of people don’t acknowledge how intelligent Arya is but when someone presents her with a goal and the means to achieving said goal, Arya can usually accomplish it, be it physically or mentally. Of course like everyone Arya has her limits and like everyone Arya isn’t good at everything, but she has perseverance and smarts. Arya may think she’s too stupid to learn and too stupid to give up, but she does learn and not giving something up is a good thing, especially in this case. The fact that the HOBAW is furthering Arya’s education and skills (most of what she is learning has nothing to do with killing and even her education around poisons and potions could lead to knowledge in healing and medicine) is going to play the biggest role in Arya’s future. Arya is naturally extroverted and charismatic and compassionate. She also knows how to rule her face, adapt, detect lies, and manipulate. The fact that she is all those things and more, that she’s a polyglot, are all good things to have when it comes to politics. Basically everything she is learning is going to make her an excellent leader and/or Mistress of Whispers and/or Ambassador.
Arya may own a sword, may know the basics of Water Dancing, may have had to fight and kill with that sword, but that doesn’t mean that that is all she is. Arya is a complex character who has many other skills, which means she’s not going to end the story as some warrior or kingsguard. She’s not going to randomly sail away an a suicidal adventure, unless like Queen Nymeria, she is sailing away with ships of refugees to find a new home.
No, if GRRM only intended for Arya to just be a “sword” or to die in the end or to just leave everything behind, he wouldn’t be wasting his time writing about Arya’s time witnessing the horrors of the War for the Five Kings. He wouldn’t be showing us Arya protecting and developing friendships with the Smallfolk. He wouldn’t be teaching her how to survive and how to grant justice and mercy. He wouldn’t be teaching her valuable potentially political tools in the HOBAW either. No, Arya’s endgame is going to be important. Maybe not the most important, and that’s fine, I’ve never thought Arya needed to end up as queen (even though she has a lot of queen foreshadowing) or “winning” in order for her to remain relevant to me or important to the narrative, but I do think she’s going to be a part of Bran’s King’s Council and she’s going to help change the face of Westeros.