The actor Sondra Locke, who has died aged 74 after suffering from cancer, was closely associated with the film star and director Clint Eastwood: they made six films together and had a 13-year relationship, which ended acrimoniously.

But it was not Eastwood who made her a star. Eight years before they met, she had already received Golden Globe and Oscar nominations for her accomplished debut as Mick, a southern teenager who befriends a deaf-mute man (Alan Arkin) in the 1968 adaptation of Carson McCullers’ novel The Heart Is a Lonely Hunter. She won the part after a nationwide search to find a suitable newcomer.

Locke also later proved herself an idiosyncratic director with the curious fantasy Ratboy (1986), in which she starred. A follow-up, Impulse (1990), a thriller starring Theresa Russell as a police officer working undercover as a prostitute, was a slicker affair.

She first starred with Eastwood in the western The Outlaw Josey Wales (1976), which he also directed. She played Laura Lee, who joins Josey (Eastwood) on his quest to avenge his family’s destruction during the civil war. “Just as he was about to look away into the distant desert, he caught sight of me,” she wrote in her 1997 autobiography The Good, the Bad and the Very Ugly. “I wasn’t prepared for the way our eyes seemed to instantly fuse.” For the next seven years, she was effectively under contract to Eastwood, who was believed to have left his wife for her. “If you were in Clint Eastwood movies, you were in the Clint Eastwood movie business,” she explained. “People stopped calling. They automatically assumed I was working exclusively with Clint.”

This translated into a period of great productivity while they were together. She starred with him in The Gauntlet (1977), as a prostitute escorted by a cop to testify in a mafia trial, and in the redneck comedies Every Which Way But Loose (1978) and its sequel Any Which Way You Can (1980) – though they were both upstaged in those movies by their co-star, Clyde the orangutan.

The couple’s most delightful collaboration was on Bronco Billy (1980), a comedy starring Locke as a woman who falls in with a travelling circus after being double-crossed by her fiance. It was much preferable to the sadistic thriller Sudden Impact (1983), the fourth in the Dirty Harry series of films about a renegade cop, in which Locke played a victim of rape turned violent avenger. That role was a curious fit for a woman whose appeal lay in her mix of the feisty and the delicate. The enormous eyes set in a petite face gave her the perpetually childlike look of one of Margaret Keane’s big-eyed child paintings. In Eastwood’s more rough-and-tumble outings she could only appear incongruous.

If Sudden Impact, their last film together, seemed brutal, that was nothing compared to the fallout from the couple’s relationship, which ended in 1989 with accusations from both sides: Locke pointed to Eastwood’s infidelities and his tapping of her phone, while he complained that his generosity was being exploited by Locke and her close friend Gordon Anderson (a childhood friend whom she had married in 1967, though he was openly gay). While Locke was on the set of Impulse in 1989, Eastwood changed the locks on their home and dumped her belongings on the lawn.

In the seven years after their split, Locke filed two lawsuits against him, first for palimony in 1989, fighting him in court for a year, all while battling breast cancer and undergoing a double mastectomy, settling in 1990; then for fraud in 1996, when a producing and directing deal at Warner Bros, which was part of the settlement in the original suit (and which spawned no movies), turned out to have been underwritten by Eastwood without Locke’s knowledge. The second lawsuit also ended in a settlement for Locke. “I think he thought I’d go away, because he always gets his way,” Locke said. “He just wills people to do things, he would say that all the time. He was willing me to go away. And I didn’t.”

She was born Sandra in Shelbyville, Tennessee, to Pauline Bayne, a factory worker, and Raymond Smith, a soldier. Her mother married Alfred Locke, a carpenter, when she was four. Sandra went to the local high school, where she met Gordon. They both enrolled at Middle Tennessee State University in 1962, but she left after a year and worked in Nashville as a TV station assistant, while acting with a community theatre group. After taking the stage name Sondra and appearing in several plays, she auditioned for, and won, her part in The Heart Is a Lonely Hunter.

Locke claimed that she was frozen out of Hollywood after her breakup with Eastwood. As an all-American hero, he was untouchable; his public did not want to hear that he was flawed. “I’m sorry he is who he is,” she said just before her book came out. “As sorry as people are going to be, it was far more devastating to me to find out who he really was.”

She made a late return to the screen last year, in a title role in Alan Rudolph’s Ray Meets Helen.

Authorities were notified of her death, but it was not made public until 13 December.

She is survived by Gordon, to whom she remained married.

• Sondra Locke (Sandra Louise Anderson), actor and director, born 28 May 1944; died 3 November 2018