Veronica's nerdy ex-friend (pre-Heathers' clique days) serves as the moral compass for the heroine as she tries to find her way back to sanity. And she's not as hot as the rest of them. So the obvious choice here would be the nerdy best friend of another dark teen angst-filled series, Jessica from "Twilight." (Note: When casting any teen show in the next 10 years, the answers lie in the "Twilight" cast). She's a pro at playing the not-as-hot (yet still hot) sidekick, so it's a logical progression.