But... But she does get angry. When Miyako eats the thingy and with the empty milk she gets "handy" with her. I know it's in a very cartoony way, but she grabs her. I'm unsure if we should count the start of this chapter, where Asako enjoys Miyako sneaking into her bed.
And the potted plant situation was ridiculous, like calm down ma'am both the book and other interwebz sources told you stuff is fine. And Miyako was even playing along for a bit, but how long can you pretend to be worried over a plant that's behaving the correct way?
Like I get what this chapter was sort of trying to get at, outside of just showing their everyday life, but it's not like Miyako killed her hamster or something. Unless it was just Miyako being a cheeky brat and wanting attention and there's no deeper meaning to it.