She is the sister of Phil Cassidy and Mary-Jo Cassidy. She is the wife of Marty Jay Williams and the mother of Mary-Beth Williams. She lived with Marty in the trailer park for the first half of the game, but then eventually moves out, taking her daughter with her, and stays with Mary-Jo in Little Havana`because of relationship problems with her husband.
After Louise moves out of the trailer park, Marty becomes angered with her act of hostility and kidnaps her in revenge. The kidnapping is alerted to Victor Vance by Mary-Jo, which Victor responds by tracking down Marty and murdering him in his own blood. After Marty's death, Louise acts as a business associate and Victor's love interest during the game, although the relationship between the two becomes sour after Victor becomes too busy to visit her.
After Marty's death, she becomes afraid that she would unable to raise her daughter properly. Victor reassures her that they don't need Marty, as Victor tells her that he would help her. Later on, Louise suggests for Victor to take over Marty's gang as a way of making money, which led to the formation of the Vance Crime Family. Shortly afterwords, she finds out that Marty's cousin attempted to burn down one of Victor's brothels and accompanies Victor to stop him. Victor also helped Louise deal with welfare that has threatened to take Mary-Beth away from her.
Later on, Victor has become busy with running his empire and working with his brother, Lance, who has come to Vice City to help Victor. Because of this, Louise has becoming lonely and angered with him., which she deals with by spending time with Lance and becoming addicted to cocaine. After Victor find out, he accuses her of having an affair with Lance and "becoming a mess", which Louise responds by saying that he didn't care for her and telling him that she doesn't want to see him anymore.
Louise fixes her relationship with Victor but she gets kidnapped by Jerry Martinez and beaten savagely by his men. After Victor rescues her and takes her to a hospital, they both apologise and make amends. After she recovers from her wounds, she goes along with Victor to rescue Lance, who was attacked by Martinez's men.
Louise is killed by Armando Mendez after Armando's men kidnapped her and brought her to the Mendez Mansion. After she is shot by Armando several times, she tells Victor before she dies that she wished that they would've had a relationship, which Victor replies that they did. She also told him that she wanted Mary-Jo to take care of her daughter.
GTA Vice City Stories
- Fear the Repo
- When Funday Comes (Boss)
- Takin' Out The White Trash (Boss)
- To Victor, the Spoils (Boss)
- Hose the Hoes (Boss)
- Robbing the Cradle (Boss)
- White Lies
- Where it Hurts Most
- Lost and Found
- Light My Pyre (Killed)