When it comes to Quinn, I really like her character, not as a person, but as a driving force in the story. I find it quite interesting how DPC made her a sort of anti-hero with the possibility of redemption, considering her actions in the last episode.
That said, I think people who debate her behavior ignore the amount of psychological manipulation, gaslighting, and how these practices, applied to people with low self-esteem or poor judgment, can distort victims' perceptions. Every day, we see real stories of people who have been emotionally and psychologically manipulated for years, not always with deliberate violence, but with subtle subliminal suggestions and under the guise of phrases like "I'm only doing this because I love you" or "I do this because I want to protect you." This is a very common strategy among sexual predators, emotional fraudsters, compulsive liars, and others.
Despite this type of predatory behavior, disguised as a survival strategy, it's more common in male/female relationships (and the news, I repeat, is full of real stories about this). I've seen and witnessed many brother/sister, father/son, mother/son relationships involving gaslighting, emotional manipulation, and psychological abuse. Such strategies are always deliberate by one of the parties, and when they occur over years, they completely rob the victim of the common sense to recognize small warning signs, because they'll always be reminded of how much the predator "does it out of love" or to "protect" them.
In Quinn's case, worse than doing this for years with Riona (and she admits this verbatim when talking to the MC, saying how easy prey she was), was her arrogance in thinking she had everything under control - an idea that was questioned more than once by Riona herself! Quinn always thought she could play chess like her father, but when things started to get out of hand, she realized how much she had let herself be carried away by her arrogance. However, by the time she realized things were getting out of hand, it was already too late, and the threat of violence and death was already knocking on not only her door, but the doors of those around her.
Furthermore, let's call a spade a spade: she's committing crimes such as sex trafficking, drug trafficking, sexual exploitation, conspiracy (if her relationship with Stephen is proven), blackmail, and other crimes I can't even imagine. In real life, she'd already be arrested, or at least on any federal agency's radar, in less than a second.
In real life, anyone even remotely suspicious of anything I've described is, in my view, a shitty human being, regardless of their childhood experiences, and I'd keep as far away from them as possible. In the fantasy world of AVN, I think I can save her from herself, and she's the best fuck I ever had!