Lilly Moscovitz is a fictional character from the Princess Diaries series created by Meg Cabot. She is best known as the best friend of the main character, Mia Thermopolis. Lilly is characterized by her strong personality, intelligence, and passion for social issues, often expressing her opinions through her popular video blog. In the series, Lilly is portrayed as a creative and outspoken teenager who supports Mia as she navigates her unexpected royal life. She is also the younger sister of Michael Moscovitz, who becomes a significant character in Mia's life. Lilly's friendship with Mia plays a crucial role in the story's development.