Justine was born and raised in England. When she was seven years old, she saw her best friend Cheryl killed when she was struck by a car while attempting to cross a busy street. The anger and loneliness she felt over her friend's death strongly influenced her. By the time she was seventeen, she had adopted a belief system which blended ecological activism with magic. She joined the environmentalist movement and began destroying cars with sledgehammers and petrol bombs.
After reading an article in Seeing, Justine travelled to the Doctor's house in Kent, where she was introduced to the Seventh Doctor, whom she believed to be a sorcerer, Ace, who scorned her belief in the supernatural, and Vincent Wheaton, with whom she began a relationship.
In New York City, the Doctor arranged for Vincent to be captured by the Butler Institute (who had detected his psychic ability) and had planned for Justine to use a drug to simulate death so that the Institute would acquire her as a source of healthy replacement organs, joining him there. However, she took the drug before he could properly brief her, forcing him to get police officers Tessa Mancuso and Breen to help Ace and him rescue her.
They took her to the Institute's site in the Catskill Mountains. The plan was for Vincent to use Justine's anger to destroy the site. This failed when she fell in love with him. Vincent used Mathew O'Hara's coldness to destroy the site and him.