It pleases me that this chapter cements that Koyuki was never a bad person.
Sure, she went about trying to make a friend in terrible way, but that doesn't mean she can't learn from this.
Looking forward to seeing how she develops from here
This is lazy and cowardly writing. You want to have someone do something bad but not have them be a bad person. So you give them a supposedly good reason, which this wasn't.
Not only was her plan insane, but she did it because she was jealous that Haimiya was getting along and having fun with Kurose instead of her.
This happens all the time in manga. It would have been far more interesting for there to be a good reason for the two to clash, real animosity and then for them to slowly become, if not friends, at least not hostile to each other.
Look at the relationship between Kuzuhana and Takae in Yankee JK Kuzuhana. They started out hating each other, but now, they still distrust and dislike each other but they are not as antagonistic and will begrudgingly help each other out.