You saying that just proves the point about looking at things in binary terms.
So, Quinn starts off at 0 for begin this manipulative character with bad intentions, but then she shows a modicum of feeling towards the MC and now she's a solid 1 and as such is now fully redeemed? Really?!
Whether in real life or in fiction, people are complex beings and not always what they appear. Most adult games do have one-dimensional, binary character, but that's because most devs aren't skilled writers and can't write complex characters, but DPC can. Quinn isn't all good or all bad, she's in the middle and as such is capable of absolutely anything, including screwing over the MC to save her own ass if necessary.
It's suspicious, given the context of events that preceded it.