That's just her competitive nature. And she's using it to improve herself. But it's not like she needlessly hates someone because they're rivals (she's friends with one of her rivals too.) It's just she's super pissed at Hishiro who's been giving her smiles that causes a lot of misunderstandings. For Hishiro, yeah she thinks she's making friends, but if someone were to give you a smile that looks like they're mocking you, you would also feel some sort of resentment. So it's not unfounded,Man Kariu should just move on. Its so annoying how she's basically dislikes people cuz they're better at something or gets salty like that. I hope she gets humiliated harder and stops being so dumb.