That might be very Tinfoily of me, or even already suggested (but the search function on the forum just doesn't work right now). I was reading a theory on the reddit in which Arya=Nissa Nissa for Jon. And I dubbed it far fetched (also, there's no "true" Azor Ahai anyway, it is known...). However the more I thought about piecing things together, the more it made sense in a way so : Arya is Lightbringer : The 2 most popular theories on Lightbringer are that or it is a literal sword