Quinn has complicated relationship with Rachel. She is her mentor, her friend and she deeply cares about her. However on occasion she can be cruel and focusing only on the show.
In season one we learned that Quinn and Chet had a marriage-like relationship for 8 years, in spite of him being married to Cynthia who is pregnant.
Death of one of the contestants made him reevaluate his life, divorce Cynthia and propose to Quinn. Unfortunately, shortly after the engagement Chet is caught in compromising situation with Maddison one of the younger team members. Quinn is furious and breaks of the engagement
In season 2 Quinn meets handsome network owner John Booth and they are quickly getting serious. She is very happy and even agree to have children (something that she did not seem interested before). Their relationship is ruined by the information that she can not carry a baby.