Kelley was a VIP hostess at the 1965 World's Fair, worked in Senator Eugene McCarthy's office in Washington, D.C. and was an editorial researcher at the Washington Post.

Her claim to fame was Jackie Oh!, the tell-all biography of Jacqueline Kennedy Onassis. Many other smut-filled scandalous biographies followed, including those of Frank Sinatra, Elizabeth Taylor, and Nancy Reagan. She also authored The Royals, which was published during the same time as the Princess Diana tragedy.