The fashion mogul hit celebrity designer Martyn Lawrence Bullard with legal papers claiming he charged her $2 million (£1.2 million) for work on her New York City apartment and Hamptons home that "would not be acceptable in a college frat house".
In the legal documents obtained by Tmz.com, Mellon accuses Bullard of leaving her home in disrepair - with broken bookshelves, peeling wallpaper, and a chandelier which was not properly secured to the ceiling - when he claimed he was finished with the project.
In addition, Mellon claims Bullard grossly overcharged, stating in the lawsuit that he billed her $35,000 (£20,545) for eight chairs purchased at a low-end store, as well as misjudging the size of a marble slab set to go into her New York City flat, so it had to be lifted via crane into the apartment. Mellon alleges Bullard charged her for the crane fee and added a 67 per cent fee for himself.
Bullard petitioned to have the lawsuit dismissed, however a judge in Los Angeles rejected his efforts on Wednesday (23Jul14).
The interior designer has had a slew of celebrity clients, including Cher, Eva Mendes and Christina Aguilera, and he was also featured on U.S. reality Tv docu-series Million Dollar Decorators, in which Mellon appeared in a 2011 episode.