Every moment with Quinn, I feel, can build up her relationship with the MC in different ways, but whichever way you go, the game has seemingly made it seem as though she likes him on any path.
travelman actually makes a good point about how she seems to enjoy a MC who doesn't give in to her provocations, resists her at every turn, and plays hard-to-get just as much as she enjoys a MC who is a bit more bold, daring, and confident at times. Since she seems to like both qualities, this seems to contradict the notion that one path has a personality she likes more than the other.
I've tended to put a lot of stock in the idea that doing things with Quinn builds the relationship with her, but looking at it from the perspective that
travelman presents it would seem that doing things isn't perhaps as important as first thought. However, this just makes this moment in Ep 6 even more jarring because a DIK MC could just do those 2 required things and be seen as playing hard-to-get and Quinn likes that, whereas a CHICK MC can do everything with her and be seen as more bold and daring which Quinn also likes, and vice-versa. So if she likes both, then what really makes the difference? If it's just him being more assertive with her when she refuses his help, well then that's very weak to have everything be undone by a simple line of dialogue.
At the very least, as I've said, she could have accepted his help and then the sex was determined by Affinity, relationship status, and the like, and on the non-sex path you'd get that double-take look she gives when she leaves where it looked like she wanted to say something as it would show she appreciated the gesture but couldn't say it.