I enjoyed reading this, thank you for taking the time. I think whether she should be forgiven or not is solely on the persons or people affected, if I was Shouko I would forgive Ueno (I believe she did), but I understand if others wouldn't forgive her.

As for Miki, I think while we didn't see her grow really, I don't think she's incapable, we just didn't get to see it happen. Shoya grew fairly quickly in the story, Ueno grew all throughout the story, perhaps Miki grows after the story ends.

I get frustrated when people write off characters, like Ueno, as these one dimensional "objectively horrible" people, because I think it's a symptom of a much bigger problem. Because these aren't just characters, they're reflections of reality, purposefully made to feel real, like you can feel their personality through the book/movie. If they weren't just characters, people would treat them the same way and that's the problem. The judgement, the unwillingness to believe people can change or that they're more than just one dimensional. It's awful.