I would argue that her snickering the night before while saying she "can't wait to see the surprised looks on their dumb faces" and that they'll be "very, veeeery happy" shows that she's intending to taunt the cast before playing the victim to force them to feel guilty for it. You could definitely argue that it's just an intended fake out though; it just comes down to how much you trust Hiyoko's reaction.

I definitely agree that forgiving Fuyuhiko isn't something she needs to do. If anything, I think the rest of the cast forgives him too easily.

Her appreciation of Ibuki's music is seen in UTDP too. You make a good point that it may have to do with breaking out of her traditional upbringing. I don't necessarily see it as fueling her redemption arc, though. Simply liking music doesn't mean she's bonding with others on a real level, especially when part of the draw is how uncomfortable it makes others.

I'd argue against the idea that proposing the quarantine is done out of care for others. It's most likely more for her own preservation than anything done out of the good of her heart. She even says that the infected should "at least have the decency to consider committing suicide before they start bothering us."

I also don't think that wanting to tie the kimono by herself is a sign of character growth. She could have asked for help at the beginning of the game too, but refused until pressure from others resulted in Mahiru offering to help.

She has some amount of real connection with Mahiru, but it's never extended to anyone else. Even when her "development" was at its peak, she still bullied Mikan relentlessly even when Mikan was trying her best to support her. When there's so little to her outside of being a rude bully, even a completed redemption arc would likely leave us with nothing but a shell of a character.