In a college full of idiots, sluts, bullies and rich assholes, Jill was a breath of fresh air. As you say she can't be considered a "typical girl next door", she is just a naive nice rich girl (too nice sometimes) who cares about the MC, without caring who he is or what fraternity belongs. I agree DPC made some huge mistakes during season 2, but overall she is, as I said before, the (almost) perfect waifu
There's no conflict in Jill's arc. This is why her entire arc is perceived as somewhat sterile and boring.
Tybalt? No one takes him seriously. No one seriously believed he could win Jill's heart. Not to mention how much DPС humiliated Tybalt the entire game.
The connection to MC's mother. But it's not a conflict. Also Lynette's diary is the most boring part of the whole plot.
Conflict with the parents over MC's past. But there isn't. He's well received.
Unfortunately DPС can't create an interesting conflict that drives the story, other than the possible cheating with Bianca. This shows his low level as a screenwriter.
You ask what would you do?
Okay, I would have initially changed Jill's character a bit. The foundation of any art is contrast.
For example, Jill could have argued with Bianca about dating MC. It could have been a bet of sorts. It would have immediately added ambiguity and drama to Jill's character, she stopped being such a one-note right and flat uninteresting character.
Sure, I agree Jill's character is a contrast in itself compared to other female characters who are sexually active. But I'd like to get a lot more out of her line than the words that characterize her, which are more like an obituary than a living person: kind, sympathetic, sweet.
Right now, the only two things that can get me on Jill's branch are the cheating with Bianca and the threesome with Bella. And he gets it.