Who is Mia Thermopolis from Princess in Pink and what is their importance?

Mia Thermopolis is the main character and narrator of Princess in Pink. She is the fifteen-year-old Princess of Genovia who lives in New York City with her mom, stepfather and cat, Fat Louie. The novel is written as a part of Mia's journal so the entire narrative is comprised of Mia's thoughts and reactions to the events that occur.