Her mother Cindy was a waitress and her father Beachard “Bill” Williams worked at an electronics manufacturing company.

[3] After college, Williams began her professional career by landing national commercials, which included Foster Grant sunglasses and TWA.

Williams accompanied an actor-friend from Los Angeles City College who needed a scene partner for the audition and was also accepted at The Actors Studio West, but rarely attended due to acting commitments.

[3][4][5] Williams picked up important film roles early in her career: George Cukor's Travels with My Aunt (1972); as Laurie Henderson, Ron Howard's character's high school sweetheart in George Lucas's American Graffiti (1973) for which she earned a BAFTA nomination as Best Supporting Actress;[6] and Francis Ford Coppola's The Conversation (1974).

[7][8] Williams met Penny Marshall, first on a double date, and later at Francis Ford Coppola’s Zoetrope company.

[12] In 1975, Williams was cast as a fun-loving brewery bottle capper,[3] Shirley Feeney, in an episode of Happy Days with Penny who played her best friend and roommate Laverne De Fazio.

[17] The premise involved Williams's character, Joanna, following her boyfriend from Los Angeles to New York, though he leaves her for another woman.

That same year, Williams starred in the sci-fi comedy UFOria alongside Fred Ward and Harry Dean Stanton, a movie which was already completed in 1981.

Williams performed onstage in the national tours of Grease, Deathtrap, and Moon Over Buffalo as well as a regional production of Nunsense.

She reunited with her Laverne & Shirley co-star Eddie Mekka in a November 2008 regional production of the Renée Taylor-Joseph Bologna comedy play It Had to Be You.