As the world knows, Paris Hilton and Nicole Richie are officially on the outs. "It's no big secret that Nicole and I are no longer friends," Hilton said in a statement last month. "Nicole knows what she did, and that's all I'm ever going to say about it."

Now that The Simple Life stars are no longer Best Friends Forever, the Hilton hotel heiress has started working the party circuit with another pop-star offspring, Rod Stewart's daughter Kimberly. At a recent event, Hilton even introduced Stewart as the woman who will replace Richie next season on The Simple Life 4.

"It's my show," Hilton told reporters, "and I want to freshen it up — make it newer and funner."

But Fox executives warn: "Don't believe what Paris says." At least not yet. While multiple sources close to the show confirm that the network is indeed retooling the rich-fish-out-of-water reality series, they stressed that Richie has not been asked to leave the cast nor has Stewart been invited to join it. "[Hilton] seems to be waging a one-woman public relations campaign," says one insider.

Both sides refused to discuss why the girls had a falling-out. (Rumors have mentioned a Richie-led public screening of Hilton's sex tape.) But insiders say if Richie does leave The Simple Life, it may be to headline her own reality show about life with her fiancé, DJ Adam Goldstein.

A source close to Richie declined to comment about either series, saying only, "Paris just likes to shoot her mouth off!"