All those questioning which three girls Burke fucked, it's very clear that the main girls in Quinn's restaurant are:
And Cammy's the newcomer who only works through the glory holes (Cammy tells the mc this when they fuck at the prep's party).
And while Quinn puts herself on the menu for the mc, it seems she doesn't offer herself up that often. She made an exception for the mc because she needed a one-off bigger cash injection, and she already kinda liked the mc.
Quinn even tells the mc she doesn't give anyone blowjobs - that doesn't mean she's never given anyone a blowjob (she obvious has, I doubt she's been practicing on a dildo all these years waiting for Mr Right), but it means it's not something she does for most guys. Now if she was prostituting herself out regularly, it means she'd be giving out lots of blowjobs for sure.
So regarding Burke, that kinda leaves us with the first three girls mentioned above: