Watching this film, I was reminded of Jane Austen's comment about her novel Emma: "I am going to take a heroine whom no one but myself will much like." Diablo Cody is very mean to her creation, but she is not mean-spirited -- a sympathy lingers around Mavis. Her neuroses are sufficiently forgrounded (to borrow a term from Harold Bloom) for the audience to understand why this person is who she is.
Jake Cole notes that the set-up of the film looks like romantic comedy, something along the lines of My Best Friend's Wedding. But Young Adult is aware of such genre conventions. It measures up fantasies of love and success against reality (family, babies, work), and portrays the damage caused by the inability to distinguish one from the other.
It's a slow build, a lot of random encounters and bitter jokes, until all the shit comes pouring out at the end. But just as the possibility for reform, resolution and companionship dawns, another conversation with a starry-eyed fan reasserts all those myths again. Cody is determined to shirk Hollywood narratives, and in the process crafts a pungent fable about how prevalent they are, how we end up leaning on them, and how they in turn end up ruining our lives.