I don't think so.
Without an antagonist, there is no conflict. Without conflict, there is no story.
Vader is an antagonist in Star Wars
The Island is an antagonist in Castaway
Death is an antagonist in The Seven Seals
The Emperor is an antagonist in Gladiator
Ted's dad is an antagonist in Bill and Ted's Excellent Adventure
Quinn is an antagonist in Being a DIK.
What's preposterous about a protagonist having an antagonist that creates conflicts for him in a story?
Comparing Quinn to the Emperor's right hand, the most feared man in the galaxy, mass murderer of Jedi and basically the face of the Empire is... extreme? Don't get me wrong, Vader is my all time favorite character but that's what's prepostorous. Quinn uses drugs, runs a "restaurant", possibly has a deal with Burke, and is basically a middle "woman" to a drug dealer. That's it. Who gets affected by her actions? If you don't want anything to do sex with money, you don't do it and it's over. If the girls don't want, they won't work. Even if they do, Camila showed us they can draw the lines. Also, there are HOTs that don't work at the restaurant so it's clear it's not mandatory as well.
Tho I gotta agree girls having sex for money in an adult game is so out of place, ikr. What's worse is you can have sex with them as well, crazy right?
If she is behind the Cathy leak/Chad stuff, then I'll agree she's an antagonist. But as of now, she didn't do anything that makes her an antagonist. Well, if I look at it now, there's nobody I can clearly call out as an antagonist. Until we discover the details of Burke's thing, nah, not really.