I think she goes for mainly two types of girls. The ones who are desperate and will accept the free tuition deal, and also the ones who are more... "liberal" with sex. Camila was basically both, she likes sex and needs the tuition.
Her dislike of Maya probably has to do with Quinn seeing through Maya's façade, that she isn't HOT material, she is attractive, but isn't a party girl like the rest of the sorority (and according to her comment when talking about them, she actively dislikes the sorority), i think that's why she is going harder on her than the others, she sees that Maya isn't truthful about wanting to join the HOTs. But of course, she needs girls and if she can use Maya's desperation? She will, of course.
Regarding Josy, Quinn just wanted to fuck with Tommy, i don't think she really cares if Josy gets on the sorority or if she fails the scavenger hunt, to say the truth.