If you believe the dark!dany thoery who do you think will end dany? Hills believes it to be arya and she did present a good arguement about it too
I saw her video! She makes a good argument, but I can't say I'm convinced. Arya just doesn't interact in any way with anything Daenerys-related. To me her arc is very much about revenge, the trauma of war, identity and getting back to her family. I don't think she has any business killing anyone important. This plotline of her becoming a ninja assassin that could then dispose of anyone she doesn't like always seemed very deus-ex-machina to me, I mean, talk about being convenient. There's a reason why George imposed a limit on the accessibility of Faceless Men (they're supposed to be SO expensive even kings would have trouble paying the fee) - because it would be extremely silly for them to be running around killing whomever.
And what thematic purpose would it serve for Dany, one of the major characters of the series, to have Arya kill her? Dany doesn't even know or care Arya exists. She may be a fan favourite, but it seems unfair to have one of your most developed characters and prophecy girl be killed by someone random to her. At least Jon Snow killing her makes some thematic sense, he is the secret Targaryen heir to throne and possible love interest, her rival/relative/lover.
I used to think that was going to be her end because of the whole Azor Ahai - Nissa Nissa imagery. The legendary hero tempers his sword* in his wife's heart in order for said sword to acquire magical properties that will help end the Long Night. But then, further east, you have the legend of the Blood Betrayal, where the Bloodstone Emperor slays his sister, the Amethyst Empress and ushers in the Long Night.
So, basically, the same act, the killing of a woman (close to the slayer) is supposed to both bring about AND end the Long Night? Seems like both acts are equally evil to me. And Davos agrees with me, what with his whole debate with Melisandre about sacrificing Edric Storm for "the greater good". So what if Azor Ahai and the Bloodstone Emperor are actually the same mythical figure and not at all heroic? I don't know.
Which is to say that maybe Dany won't die sword-in-heart. Maybe she'll have a moment of clarity where she realizes that Westeros would be a better place without her on the Throne, sacrifices herself against the Others and, in death, is revered as a hero herself.
*Also, we have this mythical sword already and there's no need for it to be tempered; it works just fine. It's probably Dawn. She even gets a close-up when Young!Elrond!Ned goes to tend to Lyanna in the flashbacks.