Jodie
Does everyone miss the point with Jodie? Her character serves as a plot devise while at the same time reflects every character flaw along the way! Every character dismisses her (and her friend by proxy) as harmless bored teens with a whistful giggle and a "Oh, remember when ____ was that age and did this, wore this, etc"
Also she is a complete contradiction: her sexual fantasy was bookended by very explicit descriptions while the actual image from her very innocent imagination was of her swooning in his arms in a long sleeved button down t-shirt! Her immature (albeit completely selfish) emails have devastating effects but move the plot along to eventually match up each character with their romantic intended.
I don't really think the "Jailbait Jodie" song was in any way meant to be literal it's a tribute. I think Ben saw in her the complete devotion he couldn't get from anyone else - seriously every woman dumps him and his friends steal them! On top of that his dog takes off every chance he gets (much to his own doggie chagrine I suspect...)