Who is Grace and Jerry from Factotum and what is their importance?

Grace and Jerry are Millionaire Willie Oxnard's girlfriends, whom he gives food, alcohol, and a place to live, along with Laura, whom Henry Chinaski meets in a Los Angeles bar. Grace is tall, Jerry is curvy, and both are in their mid-thirties, sexy, and aware of it. Grace is Willie's main girl but gives him a hard time. On his yacht, she goes into one of her moods and threatens to jump overboard, but is actually afraid of water. Laura advises Willie to give her $10. While they wait, Jerry and Grace have sex with Henry in the bunk, while Laura innocently tells them not to go too far. When Willie dies after drinking diluted vodka, Grace has to be hauled away from the brother's door by the police, whom she assaults during the arrest. None of the friends sees one another again.