Who is Nia from It's Kind of a Funny Story and what is their importance?

Nia is friends with both Craig and Aaron's. They've been classmates since grade school. She is described as pretty and outgoing, and Craig is very attracted to her. Nia and Craig remain friends even after he tells her that he is taking antidepressants. Nia, in fact, reveals that she takes them too. Over the course of the story, Craig realizes that Nia is what he believed. He gets over his crush, and subsequent jealousy, but they remain casual friends.