I just love Arya's storyline at Bravoos. What do you think of the very significant change what the show did to the Waif's character? Can we also expect a fight between the two in the books as well?
I don’t think highly of what happened with the Waif in adaptation. It’s not clear why she hates Arya or what she gets from being so antagonistic. (This is also because it’s not clear what her role in the organisation is - a senior student? If so, why are her duties mostly identical to those of a junior student, with the sole exception of training Arya?) It is clear that this change was motivated by a desire to have a “bad guy” in Arya’s TV storyline.
As for a fight between Arya and the Waif in the books, maybe. It’s one of those things that I think might happen, but doesn’t absolutely need to happen.