Symbolism, Imagery, Allegory
We already know that Jen isn't your typical teenager, and here's one more reason: she hates, and we mean hates, fake I.D.s. No sneaking out to the corner store to try to buy beer with her sister's ID for Jen. (Don't do this, Shmoopers. Big, bad idea.) See, while other shadow children are quick to adopt a false identity in order to be free, Jen thinks that fake I.D.s are "just a different way of hiding" (20.20).
And she just might be right.
As soon as we're born we're slapped with a birth certificate and Social Security Number. Want to drive a car? You have to get a license. Want to leave the country? You're going to need a passport. It's not such a big deal for kids, but adults have to prove who they are practically every day.
So we get why Jen would be passionately against fake I.D.'s. She doesn't want to get an I.D. "until [she] can have one that says 'Jen Talbot'" (20.13). At the same time, these IDs do let shadow children come out of hiding, even if it's only a little bit. When Luke is practically forced into getting a fake I.D., he's able to enter the real world where he's going to be able to continue Jen's work. Just as much as IDs represent deception and oppression, they also just might represent freedom, maturity, and a new start.