Green’s Dictionary of Slang

(US) anyone seen as disposable.

1995		S. Moore In The Cut 98: I have new words for the dictionary. [...] dixie cup, person who is considered disposable.
2000–02		Chloe Jo ‘Who’s gonna give you Fifth Avenue now?’ at ChloeJo.com 🌐 I’m Baccarat, and she is a dixie cup, and we all know it / I was your Caviar, and now you’re dining on pizza.