I'll give you my two cents on Quinn, which I still have a half hour...
her scenes are all interesting and she's a more square character than almost all the LIs who seem to be always dominated by hormone and instinct.
but she actually has a problem, which makes her difficult to appreciate.
all the female characters tend to behave exactly the same way regardless of the relationship they have with MC when they interact with other characters: Josy will always be Jill's friend, Sage will always refuse to help Maya and then try to do it later etc..
this is of course true for Quinn too, but for her it becomes a big problem, because while with MC she shows an emotional side in all the other scenes she keeps on being an undaunted bitch, which becomes hard to explain
in the last chapter Quinn emphasized her nature as the villain of the story, but it's stupid for her to keep on giving Maya a hard time, knowing that she's still a friend of MC, it's obvious that sooner or later she'll end up clashing with him, in the same way refusing to find a meeting point with Tommy means complicating the relationship between DIKs and HOTs and a Quinn who cares about MC, and who above all doesn't gain anything from this tension would have every reason to recompose the fracture.
instead no, there's no sign of change in her, Mc in the end is just a diversion in her predetermined path to damnation, at this point it becomes really difficult to believe in her possible redemption.