What scene are you referring to?
Quinn chastises Mona, and reminds her what she agreed to. Later she tells Mona to shut her mouth about the drugs, and for Lily and Camila to leave, which they do. She essentially blackmails Mona in keeping her mouth shut.
But this is really Quinn giving Mona one chance to keep her mouth shut, because if she doesn't, thanks to Stephen knowing who Mona is, Quinn then threatens to mention her to Stephen for running her mouth about soliciting sex, which would in turn likely expel Mona from the school and have a branded reputation for being a whore around B&R- which would be hard to shake.
Later in episode 6, Maya, already under the pre-tense of free tuition approaches Quinn with Mona and asks about it. Quinn then denies ever agreeing to free tuition. Mona, intimidated by Quinn caves immediately and agrees with Quinn. But Maya is having none of it--she slaps Quinn right across the face, and accuses her of lying to her and making her do some of the more unsavoury things on hers and Maya's lists--probably as insurance, if Quinn needs to use it against them. A furious Maya storms out, and Quinn doesn't say anything.
One of the end scenes is a cut to Stephen on a computer, and it shows some scholarship information with Mona's name on it. It shows that the scholarship's payment is pending, and he then deletes the information from the school's system; on the desk it shows a letter of resignation with Cathy's name on it. We then see a hooded person revealed to be Mona carrying 2 briefcases and another person following behind.
Well she lost her tuition, and she's kicked out of the school.
Yes, because Quinn and Stephen are evil manipulators.
What failure?