To say she's just a passenger is flat-out incorrect, and to dismiss that as irrelevant is flawed thinking.
I'm calling it "irrelevant" in the context of your disagreement on your own interpretation of OP's argument:-
if Karryn at some point begins to initate sex, then it's only because she was repeatedly coerced and eventually corrupted into wanting it by the inmates. I don't agree with that thinkng in the slightest though.
Sexual things being repeatedly forced on Karryn by the inmates is the only way she can turn into a slut, otherwise, she remains pure free from corruption which again, is the reason for there being different dialogue sets depending on how much she's been corrupted also leading to 2 different endings.
To imply it wasn't "forced" just because it isn't done in a generic "lose battle = get immediately raped" is objectively false here.
You'd think the prisoners would at least mention it when they take it, right?
They do mention it if it's Karryn's first time doing it.