A September court date was set Thursday in Los Angeles for diamond heiress Zeta Graff's $10 million slander suit against Paris Hilton. Graff, who used to date Hilton's former fiance, Paris Latsis, claims Hilton masterminded the planting of "vicious lies" about her in the New York Post, E! Online reported. Hilton's former publicist Rob Shuter admitted during a deposition in December that Hilton ordered him in July to tell the Post that Graff attacked the hotel heiress at a London club. Hilton reportedly admitted during her deposition that she made up the story, but denied any part in it getting out to the media. Graff's attorney said if a settlement is not reached by May 15, the case will go to trial. The court date was scheduled for Sept. 18. There was no comment from Hilton or her legal team, E! said.