Others have already written what I wanted to say, but I can add something.
I don't like how Jill took care of the MC in the first season. For example, she gathered a pedagogical council because of the MC/Chad fight and complained about it. I don't like Chad and in the end he got what he deserves according to the script, but:
1. What right does she have to decide for Tremolo? She is not his mother.
As a student and a concerned citizen, she has every right, and arguably a duty, to report Chad's actions. MC's wishes are not paramount, as much as he (or you) would like them to be. It is understandable that that would annoy one, and it's hardly endearing. No one likes a snitch, after all. But she didn't do anything fundamentally wrong.
2. It was a dangerous move and under other circumstances she would have painted a target on his back.
"Dangerous" might be an overstatement. This isn't the mafia.
And speaking of dangerous moves, how about the idea of Tremolo going one-on-one with some 'roid-raged brute twice his size? Seriously, which course of action is realistically more likely to end him up in the hospital?
3. She exposed MC as a child in need of care.
Dramatic, hyperbolic, and wrong. Given her upbringing and background, she would naturally tend to see the altercation between Chad and Tremolo as a disciplinary "law-and-order" issue for the school to handle, rather than something for Tremolo to deal with "man to man". She would probably just dismiss the latter notion as blue-collar machismo or something.
Of course, that reveals her to be privileged, strongly pro-establishment, and out of touch, which is itself something you might validly not like about her. However, framing it as some deep, hurtful, emasculating betrayal of Tremolo is uncalled-for IMO.
I have other answers that I don't like about her behavior.
And it's not hate, just fun and memes.
She does have a very memeable face.
