Lee Radziwill and Mercedes Bass are New York socialites to the bone. Ms. Radziwill, now 79, brought an element of the Gilded Age back to New York in the ’70s and ’80s: she married a European prince and was younger sister to Camelot’s first lady, Jacqueline Bouvier Kennedy Onassis. But she also stayed modern, partying with Andy Warhol and Mick Jagger, among others. The late Truman Capote obsessed over Ms. Radziwill, one of his swans, as he called the pulchritudinous women he ran with. Ms. Bass presided over the generation of New York society that followed: in the go-go ’80s, money often trumped family, and Ms. Bass quickly proved that she could rise to the top like the rest of them. Née Mercedes Kellogg, she and billionaire Sid Bass met at a party in 1986 (legend has it that she got his attention by throwing a piece of bread at him from across the room). Both were married at the time. Each divorced—Mr. Bass at a cost estimated in the hundreds of millions—and they married in 1988. Ms. Radziwill, still stylish, now lives in Paris. Sid and Mercedes Bass announced they were divorcing in 2011. Paris Hilton could learn a thing or two from these discerning doyennes.