She was the Debutante of the Decade back when debutantes were in style. But now, Cornelia Guest is a caterer. Guests at Estée Lauder executive John Demsey‘s birthday party the other night were served hors d’oeuvres by waiters from Templeton Events. Templeton is the name of the Old Westbury estate Cornelia inherited from her mother, C.Z. Guest. And as they left, guests were given a bag of Cornelia’s Cookies, which contained the advisory, “No animals were hurt while making these cookies . . . I just have a few bruises.” Cornelia, asked by Page Six if she had adopted four more dogs to bring her total to 13, said, “No, I adopted one for a total of nine.”