Keaton was born in Pine Bluff, Arkansas. She is the granddaughter of silent film Comedian Buster Keaton. She attended middle school in Eudora, Arkansas until 1960 when her family moved to Atlanta, Georgia.

In 1969, she was involved in a major car accident that left her with facial scarring. Keaton once worked as a hostess for Amtrak.

Keaton relocated to Italy in 1971, where she had signed with a talent agent, and appeared in several commercials. Her debut role was in 1972 playing the role of Solange, a missing woman, in Massimo Dallamano's movie of the giallo genre entitled What Have You Done to Solange? Though a small role, her delicate and fragile physique got immediate attention. Robert Marcucci says of her role as Solange, "She truly steals every scene she's in, simply drifting in and out of each of her scenes, her face and mannerisms mysterious and alluring." The same year, she appeared as the lead in the Italian horror film Tragic Ceremony (1972).

In November 1972, Keaton was a centerfold in the Italian men's entertainment magazine Playmen. In September 1974, she was on the cover of Playmen. Keaton returned to the United States in 1975, settling in New York City. She then appeared as Jennifer Hills, a rape victim, in the exploitation film I Spit On Your Grave (1978), directed by her then-husband, Meir Zarchi. For her performance, she won the Medalla Sitges en Plata de Ley (Sitges Sterling Silver Medal) Best Actress award at the 1978 Sitges - Catalan International Film Festival.

In 1979, Keaton married Meir Zarchi, the Director of I Spit on Your Grave; they divorced in 1982. She was married to film Producer Sidney Luft from March 20, 1993 until Luft's death on September 15, 2005. She does not have any children.

In 2012, Keaton appeared in an uncredited role in Rob Zombie's The Lords of Salem, and has also appeared in the films Chop (2011) and The Butterfly Room (2013).