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 prestigious Sadler’s Wells Ballet School to escape from an unhappy home when her parents separated in 1953. Later she attended the Corona Stage School. Her first film appearance was in the remake of The 39 Steps (1959), directed by Ralph Thomas, when she had a non-speaking part as a schoolgirl. Next she played another schoolgirl in The Brides of Dracula (1960), directed by Terence Fisher. Otto Preminger was looking for a new fresh face for the role of Karen, an ill-fated Jewish-Danish refugee girl in love with Dov Landau (Sal Mineo), for his film Exodus (1960). He travelled to Britain and Germany, with his fiance’ Hope Bryce, looking for a girl for the role. After looking at hundreds of girls, Preminger spotted a photo of Haworth in a modelling magazine for the Corona Theatre School. Haworth only went to the auditions, three of them, which included Christine Kaufmann and three other young actresses, to get out of school. She was only 15 years old when she appeared as Karen in her first acting role in a feature film. Haworth appeared in the 31 July 1960 issue of Parade magazine. Then Mineo and she appeared on the front cover of the 12 December 1960 issue of LIFE, part of a photo essay by Gjon Mili. Under contract to Preminger (for five years), she also worked with him in The Cardinal (1963; as Lalage Menton), and In Harm’s Way (1965) as Ensign Annalee Dorne, a Nurse Corps officer who, while engaged to Ensign Jeremiah ‘Jere’ Torrey (Brandon deWilde), commits suicide after being raped by Captain Paul Eddington, Jr. (Kirk Douglas). Haworth liked working with De Wilde, Patricia Neal, and Douglas, but called John Wayne “the meanest, nastiest man with the worst attitude I ever worked with.” (A month after filming concluded, Wayne was diagnosed with lung cancer and had a lung removed.)

Preminger insisted that she live in New York City to become Americanized, but he did not want her to live in Los Angeles for fear she would just be a ‘starlet a-go-go’. She was approached to be the title character in Lolita (1962) with James Mason, but because Preminger held her contract, he vetoed the idea. Mineo and Haworth were also considered for the film David and Lisa (1962), but once again Preminger refused permission. Preminger did 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). Also 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 film The Greatest Story Ever Told (1965). She made four appearances on the TV programme 12 O’Clock High. In the first season, fourth episode (“The Sound of Distant Thunder” – 1964), she played an English girl, Mary, who falls in love with Lieutenant Andy Lathrop (played by Peter Fonda). The following season, she played a deaf girl, Nora Burgess, in an episode entitled “To Heinie with Love” (1965). She then played Lieutenant Fay Vendry in two episodes, “Runway in the Dark” (1965) and “The Hotshot” (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, “Duel at Daybreak”, of the series Rawhide as Vicki Woodruff, where Haworth just “adored” Charles Bronson, but Clint Eastwood snubbed her and did not say two words to her off camera. 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. She starred in the horror films It! (1966), The Haunted House of Horror (1969), Tower of Evil (1972), Home for the Holidays (1972), and The Mutations (1974). She only did It! for the money, hated her hair in the film, and hated the film altogether. Haworth liked working with Roddy McDowell, who brought her the poster for the film (on her opening night of Cabaret), and wrote “S-h” in front of the title. 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 and she responded, “Louder than Merman.” She played Sally Bowles in the original Broadway cast of the 1966 musical Cabaret, a part she played for two years and four months. Judi Dench took over the role when the production debuted in London in 1968. Haworth’s other theatre roles included the plays Bedroom Farce and Butterflies Are Free. Haworth turned down working on Hawaii Five-O because of the reputation of the show’s star, Jack Lord, for being a hard-driving perfectionist.

While making Exodus, Haworth became friends, first, and then lovers, with Sal Mineo, and they were friends until his death in 1976. She lost her virginity to Mineo at the age of 15 in her hotel suite at the Gotham Hotel in Manhattan. Their relationship as a couple ended on Valentine’s Day 1964. She did not talk to Mineo for a time, but they eventually became friends again, made public appearances together, and in 1971 she invested in his attempted production of The Wrong People (a book about a homosexual relationship with a young boy). Their friendship even led to a brief resumption of a sexual relationship in 1969, but after she got pregnant in September and had an abortion, they went back to being just friends. Haworth 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 dated television producer Aaron Spelling in the summer of 1965, when he was 42 and she was nearly 20. Spelling told friends that he hoped that Haworth would be the next Mrs. Spelling, but Haworth’s mother, Nancy, “scoffed” at the idea and told the press that she was dating lots of guys and was in love with a different one every week. Though Haworth and Mineo were not a couple, they were still friends and he was very protective of her. He found Haworth and Spelling together at a Beverly Hills private nightclub called Daisy, and walked up and punched Spelling in the face, yelling, “Do you know how old she is? What are you doing with her at your age?” She went on the daytime talk show Girl Talk, hosted by Virginia Graham, to talk about the accident that she had had on the set of Rawhide, and they had also booked Mineo on the show, as well. The host asked her why Mineo and she had broken up and she just blurted out, “Well, he left me for another man.” Nobody seemed to catch it. Haworth lived in New York City, on the 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, and is buried at Kensico Cemetery.