Symbolism, Imagery, Allegory
Okay, this is an obvious one, but the blossom that grows out of Laurel's back (that also resembles wings) is a pretty powerful image in the book. To Laurel, it symbolizes how her life has gotten out of control and freaky; to David, it symbolizes how she is unique and beautiful; and to Tamani, it's just another normal part of her being a grown-up faerie.
Once Laurel learns from Tamani that she's a faerie, and faeries are plants instead of animals, the blossom becomes a sign of her true nature. Tamani explains: "You're a plant. You're not human, never have been. Blossoming is only the most obvious manifestation" (8.100). From this perspective, it makes sense for Laurel to blossom, since she's a plant and thus tied into the cycles of nature. And, of course, by connecting with her faerie identity, you could also say Laurel is blossoming metaphorically by becoming more fully herself.
The fact that humans tend to misinterpret the blossoms as wings (when they see faeries at all, that is) represents how mysterious and unknown faeries are to humans. Tamani tells Laurel:
There are no wings, Laurel. Not on anyone. Some blossoms resemble wings, the way some flowers resemble butterflies—your blossom was pretty wingish, actually. But they're just flowers, as you've discovered. (13.79)
The blossom, in essence, connects Laurel to nature, and the fact that it looks like wings is incidental. This is a reminder that Laurel's a lot closer to nature than humanity, even though she doesn't realize it at first. Her body has always shown the signs of natural adaptation through her food preferences, but when the blossom emerges, it becomes impossible to ignore the fact that Laurel isn't exactly your average teenage girl.