When early financial backers of Marlee Matlin’s new film, Coda, expressed their preference for hiring big-name actors to play the roles of two major deaf characters – her onscreen husband and son – she threatened to quit. She told them that deaf actors should play characters written as deaf. “I said: time out. This is not right. It’s not authentic and it’s not going to work. If you go down that route, I’m out, because I don’t want to be part of that effort of faking deaf. I’m glad they listened.”

I can’t imagine anyone not listening to Matlin. Speaking from her home in Los Angeles, she is funny and warm, but there is something intense about her, almost intimidating. She sits straight-backed, her focus sharp. She is not a woman to mince her words – which are translated from American Sign Language (ASL) by her longtime interpreter and producing partner, Jack Jason, who is also on the call from his front room. The pair have been working together since 1985, just before she won the best actress Oscar at 21 for her first film role, playing a young deaf woman in the 1986 drama Children of a Lesser God – beating Sigourney Weaver (who was up for Aliens), Jane Fonda, Kathleen Turner and Sissy Spacek.

Matlin, 55, is still the youngest best actress winner and the only deaf actor to win an Academy Award. On TV, she has picked up four Emmy nominations – one for her role in the all-time classic Seinfeld episode The Lip Reader, playing Jerry’s girlfriend. In The West Wing, she played the pollster Joey Lucas. She is now working on a project about how Prince Philip’s mother, who was deaf, rescued a Jewish family during the second world war. As an activist, Matlin helped push through legislation in the US requiring closed captioning on TV and streaming sites. She can’t stand inequality, in her own life or anyone else’s.

She says she is still boiling at a spiteful comment in 1986 by the film critic Rex Reed: “[He said] I won out of pity – that I was a deaf person playing a deaf role, how is that acting?” Her eyes widen. “There are hearing people playing hearing roles; how’s that any different? That’s what we call ableism, or audism.” In her 2009 memoir, I’ll Scream Later, she illustrated the incident with a photo of herself asleep as a child, bare bottom in the air, captioned: “Kiss my ass Rex.”

How did those comments make her feel at the time, when she was meant to be enjoying a delicious moment of success? “They were trying to make me feel less-than as a person, ‘handicapped’, that I wasn’t even able to do the work that I passionately loved to do,” she says. “They were telling me no, that I should not be able to be in Hollywood. Who are they to tell anyone that? How dare they?”

Self-belief, and an instinct to prove people wrong, has been there since Matlin grew up in middle-class suburban Chicago. She was born hearing and became deaf at 18 months; in her early 40s, a doctor told her the cause was probably a genetic condition. A happy kid, she had lots of friends and a determined streak: “If I had my mind on a candy bar, I would get a candy bar. My drive was huge.”

Matlin says she also had a temper and would get frustrated seeing her two older brothers playing music or picking up the phone to their grandmother. In retrospect, she believes she was angry at the ways being deaf isolated her. But, at about 11, something changed. “It was just a realisation of what my identity is,” she says. “I knew that there was a big world. I knew somehow in my gut that I had bigger fish to fry.”

Matlin went to a mixed deaf and hearing school and started acting at seven. When she was 12, Henry Winkler and his wife came backstage to meet her. Winkler became her mentor: “My Yoda”. When she moved to LA in the late 80s, she crashed in the Winklers’ pool house and ended up staying there for two years. She got married in their garden to Kevin, then a cop, whom she met in uniform, working on the set of a film. They have four children.

Listening to her gut doesn’t always make Matlin popular. In 1987, fewer than 48 hours after winning the best actress Golden Globe for Children of a Lesser God, she checked herself into rehab. She had started smoking weed just before her first year of high school and could puff through 20 joints a day. Now she was taking cocaine.

Her parents, her agents, everyone, said it was the wrong time to get clean. “No one wanted me to go into rehab, because I had just made a movie and the potential of getting an Oscar was going in my direction,” she says. “And I said: ‘Yeah, but to keep going I need to take care of myself first.’ I had to get sober so I could think clearly.” Matlin was in the Betty Ford clinic when she found out she had been nominated for the Oscar.

On the night Matlin won, she was clean and sober, but her dream-come-true moment ended miserably – with an emotionally abusive outburst by her then-boyfriend, William Hurt, who co-starred in Children of a Lesser God. He was also up for an Oscar, but missed out. He had been dreading her winning. In I’ll Scream Later, she described getting into a limo after a party, shiny gold statue by her side. Then Hurt got in the car and started laying into her verbally: “What makes you think you deserve it? There are hundreds of actors who have worked for years for the recognition you just got handed to you,” she remembers. “Think about that.” He then told her to sign up for acting classes.

In the book, Matlin detailed the physical and emotional abuse she endured during their two-year relationship. The pair met on the set of Children of a Lesser God; she was 19 and Hurt was 35. By the time of the Oscars, they were media darlings – the onscreen couple who fell in love for real. But Matlin wrote about arguments that turned violent, that left her with bruises and cuts and, on at least one occasion, fearing for her life. She also wrote of one incident of sexual violence, after Hurt staggered into their apartment drunk at 4.30am.

Responding to Matlin’s memoir, Hurt said in 2009: “My own recollection is that we both apologised and both did a great deal to heal our lives. Of course, I did and do apologise for any pain I caused. And I know we both have grown. I wish Marlee and her family nothing but good.”

I ask Matlin if she found it painful to write these sections of the book. She shakes her head and fixes me a steady look with her shocking blue eyes. “I could not wait to tell my story, to talk about what I went through,” she says. Did she worry her revelations could damage her career? “I didn’t even give it a second thought, because it was the truth. It was my truth – and up to me to tell it my way.”

Matlin’s account of her relationship with Hurt was not widely reported when the book came out, but she got letters from women who had been through similar experiences. How did she feel a decade later when #MeToo exploded? “I felt a vindication. I could understand the anger. I could understand the cry for help. I applauded each person who came out and talked about their experiences and understood that it isn’t easy. People got blacklisted – it happened to some of those actresses. If it happened to you, have a right to talk about it.” She also writes in the book about two sexual assaults in her childhood: the first by a female babysitter and the second by a teacher – whom she later learned was a repeat offender.

Behind Matlin, I can see honours and awards. Is her Oscar there? No, it is in the dining room. “Get it for me, please,” she says, looking away from the camera. Kevin, it turns out, has been in the room all along. While he is gone, Matlin tells me he recently broke his collarbone. “He’s just had surgery. So I’m making him lift an eight-and-a-half pound [3.9kg] Academy Award.”

I see Matlin’s funny side when her husband returns and she mimics a shocked and delighted I’ve-just-won-an-Oscar face and starts lifting her statue like a dumbbell. She certainly gives a terrific comic performance in Coda, a heartwarming and funny family drama set in a Massachusetts fishing community. It prompted standing ovations – and a bidding war – when it premiered at Sundance.

The title is an acronym for children of deaf adults – used to describe hearing kids who grow up with deaf parents. Emilia Jones plays teenaged Ruby, the only hearing member of her tight-knit family. Matlin plays her mum, Jackie, who is baffled when Ruby joins the school choir and discovers a talent for singing (“If I was blind, would you like to paint?” she jokes. Matlin says it was the hardest line for her in the film.)

The film is a portrait of the lives of deaf people. One of the loveliest moments comes when Ruby’s singing teacher asks her to describe how music makes her feel. The question stumps her; she can’t find the words. Then she thinks for a second and signs her reply. For her, ASL is the language of feelings and expression.

What Coda doesn’t do is treat deaf culture as something that needs to be “fixed” – a criticism many deaf people levelled against Children of a Lesser God when it came out. That film featured Hurt as James Leeds, a trendy hearing teacher who gets a job at a deaf boarding school and shakes things up. Matlin’s character, Sarah, is a brilliant but damaged ex-pupil, now working as a cleaner in the school. Hurt has more screen time than Matlin and is a saviour figure to the deaf characters. Rather than captioning Matlin’s lines, the script had Hurt speak them back to her.

Children of a Lesser God is Matlin’s proudest achievement, but she says it would be done differently today, “with all the awareness of how it’s OK to subtitle, and I think that probably the perspective would be Sarah’s instead of James’s. A lot of deaf people would totally identify with the story of Sarah more than perhaps in the original film. But it was beautiful in the fact that it was cast authentically. And I think that we need more stories like that, on television and in film.”

And deaf characters must be played by deaf actors. “Enough is enough. Deaf is not a costume. It’s not authentic and insults the community that you’re portraying. Because we exist, we deaf actors. We do a much better job of portraying characters, telling stories that involve deaf characters, because we lived it. We know it.”

• Coda is in cinemas and on Apple TV+ from 13 August