Locked in Azkaban (A Harry Potter Fan Fiction)

When a girl from Harry Potter's past returns into his life things turn suspicious. This girl was once the best friend of Harry Potter and had her whole life ahead of her. Her parents always traveled on business but the girl never knew what they did. She was finally brought into Hogwarts but Things start getting fishy when dementors turned. The Life of the young girl Phoenix took a dramatic turn once she entered the Hogwarts school grounds. Can Harry, Ron and Hermione help her?