Her friends once called her the Oxford hermit, but since her book “Georgiana, Duchess of Devonshire” has been turned into a movie starring Keira Knightley and Ralph Fiennes, Amanda Foreman has transformed into a social butterfly.

At the new (as-yet-unopened) Cooper Square Hotel on Wednesday night, Ms. Foreman — whose brother Jonathan is a film critic for the New York Post, and whose late father Carl Foreman wrote the screenplays for “High Noon” and “The Bridge on the River Kwai,” among other films — joined the actors for a screening and party. Yesterday she took the spotlight on her own at a luncheon hosted by another writer, Danielle Ganek, at her art-filled home at 740 Park Ave. Tonight she’ll be talking about the film after a screening at the Museum of Modern Art.

The luncheon brought out an accomplished group of women who, like Ms. Foreman, would find much to admire in the biography of Georgiana, who was, incidentally, an ancestor of Princess Diana.

“There must be some weird genes in the Spencer line, because they’re both fascinating women,” Ms. Foreman said.

Guests listened intently as Ms. Foreman gave a sketch of Georgiana, played by Ms. Knightley in the film. She married the Duke of Devonshire, played by Mr. Fiennes, at age 17, and was thrust immediately into social stardom. “When she wore blue, everyone wore blue,” Ms. Foreman said.

However, with a “damaged and damaging mother” and a “needy husband,” Ms. Foreman said, the duchess suffered. She had an affair and a child with Charles Grey, played by Dominic Cooper in the film. Her husband gave her the choice to either go with Grey or stay in the marriage with him; but if she chose to stay, he insisted she go into exile and never see her child again. “She made the brave choice, and went into exile,” Ms. Foreman said.

The film itself focuses on this crisis in her life. But Ms. Foreman made it clear that the potential for sequels is strong: Georgiana returned to England and developed an eye infection that left her blind in one eye and scarred. Her friends thought she’d give up on herself. But instead, she went through a three-year rehabilitation — healing herself of bulimia, gambling, and drugs — and re-entered society, achieving social and political success. And she did it all without Botox.

Some of the guests asked Ms. Foreman if she planned to develop an obsession with a new female subject. “No, I think I’ve found the one for me,” she said.

agordon@nysun.com