As you note yourself, during that particular talk Maya didn't agree to anything, but also Quinn never explained what she expects the pledges to do. So it's quite reasonable to presume there was another talk between them afterwards. One that didn't get interrupted, and which helped to hash these details out, including Maya's agreement to participate. Otherwise, at the very least we have a mysterious case of psychic Mona who somehow got an idea all on her own that she's supposed to talk with Burke about her "free tuition" during the party orchestrated by Quinn.
Quinn also never dispels the alleged rumor while baiting Maya and Mona, even though it'd be perfectly normal thing to do if it's just a false rumor, unless you're trying to fool people into believing it is true. She also never corrects Mona's idea/statement this is offer of free tuition, which, again, would be expected unless one was trying to make advantage of such mistake. Am pretty sure we both know it, and you're using the same silly tactic Quinn used herself, excusing her on technicalities from situation which was clear to all involved.
Yes, such great teasing, making people participate in filming porn and potentially whore themselves out with college staff, taking advantage of their financial situation. 10/10 joke.
Frankly, Quinn was very lucky to get away with just a simple slap for her "prank". Picking up teeth from the floor and another bloodied nose would be more in line in terms of payback.