Socialite and designer Nicky Hilton lashed out at actress Mischa Barton at a recent Hollywood party, calling THE OC star a "fat cow".

The 20-year-old younger sister of Paris Hilton was one of many stars at power manager Benny Medina's 48th birthday celebration.

Slender Mischa, whose ex-boyfriend Brandon Davies has also dated Hilton's sister PARIS, shrugged off the insult by saying, "It probably says more about her than me."