There is something to be said about Teddy, although by the end of the novel, the reader is more aware of Naomi alone than they ever were of Teddy, but still, Teddy's symbolic value is essential to understanding the plot. The way Naomi utilizes her relationship with Teddy shows us everything about her family's brokenness. She goes to Teddy for friendship, for romance, and for communion. That means that her parents don't understand that they not friendly toward her, that they don't give her the love and support she requires to be healthy, and that they become private instead of talking through their problems.
These factors give Naomi a very specific set of desires, and when she accidentally makes a bunch of friends in college, she realizes by the end of the story what the reader could have known just by how she treated Teddy. She is truly desperate for human love and approval, but then again, she feels loved and approved when she sacrifices for her friends, so she tries to save them from their fates. But it fails, and she is left back at the drawing board, so to speak, scratching her head trying to figure out where she mis-perceived what friendship was supposed to be about.
The answer is that she really was not old enough to be "in love" with Teddy. When she and Teddy decide to become their own little family, that is not a sign that their home lives are functional, so whatever she is looking for in Teddy, she is not finding in her parents. That leaves her with the impression that she needs to replace her parents' love. But, perhaps if Naomi could ask a person whose family doesn't have the same dysfunctions or tragedies, she would learn that they too struggle with loneliness. If friendship isn't about saving each other, and if orphans and well-parented people are all lonely anyway, then what is the sum total of all of these riddles? It is that Naomi wants her own love and approval, and she will have to deliberately give it to herself, because her parents cannot save her, just like she cannot save them. She can however learn to give herself all the love she requires.