Phoebe is rich and from an important family. Mallory is poor; a nobody. Phoebe is ordinary in appearance; Mallory is stunning. Phoebe has loving parents; Mallory's single mother is mentally ill. Phoebe is kind and warm; Mallory is cynical and suspicious. Phoebe is open; Mallory lies about everything.
Phoebe is human. Mallory is fey, and charged with an urgent mission from the Faerie Queen: to destroy Phoebe, the friend she has come to love.