I'll take the exact opposite position and say that the people who are "delving deeper into her motivations" are missing out on a large part of the story because they are too busy desperately searching for excuses for Quinn's horrible behaviour. The most common of which is framing her as a sympathetic victim of circumstance because she came from a broken home, which works because the knee-jerk reaction to hearing that someone had a hard childhood is to view them with pity and sympathy.
Yeah that's the stuff I'm talking about right there.
Dude... we've seen her slap Riona across the face, we've seen her tell Riona that she's too stupid to pass college on her own in order to keep whoring her out, and we've seen her ridicule Riona's fears of being stalked when Riona came to her for help. How can you possibly think that Quinn's actions are to protect Riona?
Quinn betrays people who are dumb enough to trust her. That's an ongoing theme in the game, and a core aspect of her character. Quinn betrayed Tommy in order to try to sell drugs to the preps. She betrayed Sage in order to whore out the HOTs and use them as an opportunity to sell drugs. Quinn will tell you that Camilla was the one in the glory hole (if you took that route), even though Camilla only agreed to work for Quinn if she was anonymous. One of the very first things Quinn does in the game is blackmail the MC into stripping naked under threat of screaming for help and calling him a pervert, and when he complies, she not only breaks her word but also pushes him out into the streets naked. She's been betraying people the entire game. Often just for the fun of it, which is something she has flat out told us in the first episode.
Hurting the people she likes in order to control or punish them is another well established aspect of Quinn's character. Quinn tasered the MC in the throat until he passed out, and she will knee him in the balls if he refuses her sexual advances. So her slapping Riona is par for the course. But somehow you are trying to spin things so Quinn striking Riona is an example of Quinn protecting Riona? That's ridiculous. Riona was the one trying to protect Quinn, by telling her not to bring in Maya and Mona. And she was right. Quinn will now be under scrutiny from Sage because of what happened with Maya and Mona, which is going to make things real hard to pay off their drug debt. Which is an even larger problem now that Quinn managed to lose her last pickup.
We don't need to know every single detail of Quinn's life to know what kind of a person she is, because she's already demonstrated that quite well. Quinn is trash. She is the trashiest character since Marjory from Fraggle Rock. Actually... that's unfair to Marjory, as although she was a literal trash heap, she was a kind soul who helped those in need. Quinn is the exact opposite of that, which actually makes her trashier than a talking trash heap. Tommy was worried about Josy joining the HOTs, and Quinn used that as an opportunity to tease him instead of reassuring him by offering to look out for Josy. Maya went to Quinn for help with tuition, and Quinn lied to her and tormented her for her own amusement. And we've already talked about how Quinn takes advantage of Riona's vulnerabilities.
There is no hidden backstory that could possibly justify Quinn's treatment of others in this game. Her personality is very clearly established already. What exactly are you waiting to see? Are you expecting to learn that some supervillain is magically forcing Quinn to treat every character in the game like shit?
Delving deeper into a character requires some sort of evidence from the game that will support you arguments. You can't just say that your interpretations are equally valid because the game isn't over yet so the author could still pull any number of plot twists out of his ass. Imagine that there were two people who see an animal that looks like a duck, walks like a duck, and quacks like a duck. One guy says that it's clearly a duck, and the other guy says that we can't be sure because we haven't seen if it swims like a duck yet so there's still a chance that it could be a giraffe. Would you say that those are equally valid interpretations? I wouldn't.
