The girl's name is Mia Thermopolis, and she lives with her artist mother in a small apartment in San Francisco. She struggles to fit in at school and is often teased by her classmates. One day, her estranged grandmother, Clarisse, comes to visit and reveals to Mia that her father, who she believed was dead, was actually the crown prince of Genovia.
Clarisse informs Mia that she is the only heir to the throne and must attend "princess lessons" to prepare for her coronation. Mia is resistant at first, but as she learns more about her heritage and the responsibilities that come with being a princess, she begins to embrace her new role.
As Mia navigates her new life as a princess, she also discovers a romantic interest in her classmate, Josh, and must learn to balance her royal duties with her personal life. But when a scheming member of the Genovian parliament tries to overthrow Mia and take the throne for himself, she must use her wit and determination to save her country and prove herself as a true princess.
Throughout the movie, Mia learns important lessons about self-confidence, friendship, and the power of being true to oneself. The Princess Diaries is a heartwarming coming-of-age story that has become a beloved classic for audiences of all ages.