Haworth was born in Hove, Sussex, to a textile magnate father and a mother who trained as a ballet dancer. She was named Valerie Jill in honour of the day she was born, Victory over Japan Day or V.J. Day. She took ballet lessons at the Sadler’s Wells Ballet School to escape from an unhappy home when her parents separated in 1953. Later she attended the Corona Stage School.

Mineo and Haworth were also considered for the film David and Lisa (1962), but once again Preminger refused permission. Preminger let her make three French films; Les Mystères de Paris (as Fleur de Marie; 1962), Because, Because of a Woman [fr] (as Cécilia; 1963), and Ton ombre est la mienne (as Sylvie “Devi” Bergerat; 1963). Haworth co-starred alongside David McCallum in the Outer Limits episode, “The Sixth Finger” (1963). Haworth visited Mineo in Utah in November 1962 and had a nonspeaking role as an extra in The Greatest Story Ever Told (1965).

In 1965, she appeared in an episode of The Rogues entitled “Mr. White’s Christmas” as Timothea, and really loved working with David Niven and Charles Boyer. She appeared in one of the final episodes of the series Rawhide, “Duel at Daybreak”, as Vicki Woodruff. Haworth first hurt her back in an accident on the set when she jumped from a runaway buggy and team of horses. She then caught pneumonia and was bedridden for two months after she had to stand waist-deep in a man-made pond for six hours doing retakes.

While filming It! she met Hal Prince, who was doing research for a musical based on Goodbye to Berlin by Christopher Isherwood. Prince asked her if she could sing, to which she claimed, “Louder than Merman.” She played Sally Bowles in the original Broadway cast of the 1966 musical Cabaret, a part she played for almost two and a half years. Judi Dench took over the role when the production debuted in London in 1968. Haworth’s other stage roles included Bedroom Farce and Butterflies Are Free.

While making Exodus, Haworth became friends, first, and then lovers, with Sal Mineo, and they remained friends until his death in 1976. She later told author Michael Michaud that she thought Courtney Burr III, who later had a long-term relationship with Mineo, was the “love of Mineo’s life.”

Haworth lived on New York City’s Upper East Side for many years with her mother. She died of natural causes at the age of 65 on 3 January 2011 in Manhattan. She is buried at Kensico Cemetery.