I think GRRM would likely flesh her reasons out more if this is the route they go down. From what some book devotees have said, there's a good chance her story there will have many different turns anyway - for instance, some of them feel Missandei (who is much younger in the books) is a spy.
It seems like D&D are doing what they've done for years, are sort of grinding out story beats they think fans want to see, or for the sake of "moments," whether the moments are earned or not. The Hound telling Arya that she must not choose vengeance and must now move on, even though Arya has already slaughtered countless people, including nearly an entire family (the Freys), and logically is long past the point of her "father" telling her to be a good person. Or Jaime deflowering Brienne and then dumping her to go die with Cersei. It makes sense that he would want to go die with Cersei, but why was there ever a need for any of that with Brienne? Was it supposed to be a sop to "Bramie" (or whatever they are called) fans? Was it meant to be some kind of added pathos? Was it supposed to be a fakeout? Would the story have lost anything if Jaime and Brienne had remained platonic and Jaime had simply left a pining and stoic Brienne at Winterfell as he went to die? And then there's Jon, who has no real voice or role beyond, I guess, waiting around to kill Dany?
I've seen a lot of fans saying they don't care what Dany did and they were fine with her killing thousands. That makes sense, in a way, because they know her, they don't know extras and bit players, but it also shows how hollow many of the emotions and characters and constructs have become when more people don't react to what is a grotesque war crime.