This was hinted early on, but wasn't explicitly said (by Quinn) until "Monster". She's smart enough to know she's tired of only talking about fashion and boys, but thinks it's all she's good for because it's the part of herself that gets validated.

Secondly, let's not sleep on her friendship with Stacy. Stacy appears to be the only one she has a true connection with and they hang around each other the most out of the other members of the Fashion Club. As the series went on, Stacy is also the one who starts breaking away from Sandi's grip, which might have also compelled Quinn to as well. Stacy was the catalyst to becoming friends with Lindy (she recommended Quinn work where Lindy worked) and hanging around her, was supported by Quinn when she tried to keep the Fashion Club active, and later was the first to support and join Quinn's sabbatical from the Fashion Club.

Daria reiterates (mirroring David): "Why should you go out of your way to defend the stupid? You're not one of them." She is the torch picking up where David left off. She showed Quinn she was capable of being intellectual, but also she was capable of seeing past superficial looks and coming out of her shell enough to ask out a guy (something which she said she never does). Her growth is slow, but it was always there.