You have to be one hell of a performer to take the title role in a film called A Fantastic Woman and convince the world that, yes, your character truly is a fantastic woman and you are too. And if you’re a largely unknown actor in only your second movie, it takes some quite remarkable self-assurance. But, a decade after transitioning as female, and a year after her breakthrough role dazzled the Berlin film festival, Chilean newcomer Daniela Vega is fully enjoying the rewards of being fantastic and on her own terms. She didn’t model her character in the film on any screen stars, she says, and the same goes for discovering her own identity as a woman. “Soy muy yo,” she says – “I’m very much me.”

Directed by Sebastián Lelio , A Fantastic Woman, the follow-up to his acclaimed female-centred drama Gloria, has been the toast of the festival circuit over the past year and is now heading for the Academy Awards, where it’s up for best foreign language film. It’s a magnificent work, stylish, playful and highly serious and, despite its protagonist’s sometimes harrowing ordeals, exuberantly uplifting. But what seals the film’s brilliance is Vega’s extraordinary portrayal of Marina, a young trans woman facing intense social hostility. It may be that, as Juliet Jacques suggested in a recent Guardian article, that in playing someone whose experience is in some ways close to hers, a trans actor such as Vega is able to bring a special bonus of “emotional memory” to her performance. But regardless of the viewer’s curiosity as to whether or not Vega essentially “is” Marina, there’s no denying that she brings a depth, sophistication and resilience to the role.

Lelio’s film has been widely acclaimed not just as a superb work, but also as a rare screen depiction of a trans heroine that casts a trans woman in the lead. We’re used to seeing cisgender actors, male and female, winning plaudits for playing trans roles, whether it’s with the subtlety of Felicity Huffman in Transamerica or the coy awkwardness of Eddie Redmayne in The Danish Girl. But we’re also witnessing a period in which trans roles demand trans casting, as in Sean Baker’s Tangerine or in Orange Is the New Black, which got actor Laverne Cox on the cover of Time magazine. There are also precursors such as Spain’s Antonia San Juan, with her immortal onstage monologue in Almodóvar’s All About My Mother: “Soy muy auténtica” (“I’m the real deal”).

These latter performers, however, have played socially marginal characters in larger-than-life dramas, respectively, sex workers, a prison inmate, a stage bohemian. What’s different about A Fantastic Woman is that its heroine inhabits a world of everyday tribulation, living an unsensational life defined by work, love and bureaucratic obstacles. Vega plays Marina, a waitress and singer engaged in a relationship with an older man, Orlando. Then, when crisis hits, Marina becomes an object of baffled, wary inquiry by the Chilean authorities and the object of bitter hostility from her partner’s family.

When I meet Vega in London, it’s clear that she’s taken to the spotlight like a natural. Sitting in Hazlitt’s hotel and speaking Spanish with an interpreter present, she projects an altogether classic image: crisp white blouse, full skirt, pearl necklace, pumps, the composure of someone who’s totally at ease in the spotlight. She has a dash of grande dame hauteur, but there’s also impish wit. When I pass her the plate of biscuits on the table, she says in English: “My waist is telling me no.”

Vega makes it clear that, along with its emotional charge, A Fantastic Woman also has a strong political agenda with regard to trans identity. “The film wants you to question where you stand in society. Are you with Orlando’s family or with Marina? Instead of answering questions, the film’s trying to ask questions about everything. What bodies can or can’t we inhabit? Which love stories are valid and which aren’t? Why is it that certain groups oppress other groups because they’re not within what they consider normal boundaries?”

Before A Fantastic Woman, Vega had previously appeared onstage as an actor and singer and appeared in one Chilean feature, as well as various music videos. But it wasn’t initially her experience that led to her being cast as Marina. Lelio and co-writer Gonzalo Maza had been working on their script for a while but realised they didn’t know any trans people in Chile. They needed a consultant and someone suggested Vega. So did the character of Marina in some ways become her?

“Sí,” she says emphatically. “Sebastián invited me for a coffee and when we met it felt like we’d always been friends – we established a friendship that developed over a couple of years.” There was no suggestion that he wanted her to act in the film; she didn’t even know what the story was about. “Then one day a package arrived at my place and when I opened it, it said, ‘Una Mujer Fantastica’ and in brackets, ‘Top Secret’.” After reading this early draft, she called Lelio in Berlin, where he lives. “He said, ‘OK, it’s about time I told you – I want you to be the lead.’ I said, ‘You’re crazy.’ He said, ‘No, I’m completely certain.’ And I said, ‘OK, I accept.’” More precisely, Vega went away and partied for three days, then said yes.

One thing that makes A Fantastic Woman so fascinating is that it denies us the conventional gratification of a back story. Of course, we’re curious to know how Marina and Orlando met, and we may want to know Marina’s history, complete with the details of her transitioning. But, the film elegantly but firmly tells us, none of that is our business: as with Marina herself, what concerns us is what we see in the present. “Of course,” says Vega, “I imagined a background for the character, but that’s a private creative process between the director, my co-star [Francisco Reyes, who plays Orlando] and me.”

Daniela Vega as Marina in a scene from A Fantastic Woman.

Working with Vega as consultant, Maza tells me later, was a process of discovery; she put him and Lelio through what he describes as “transgender for dummies.” They learned that “it’s very rude to ask a transgender person whether they’ve had surgery. Daniela said, ‘It’s up to me whether I did or not, but you don’t ask.’ And we put that in the film.” Indeed, Marina constantly encounters, and resists, the intrusive curiosity of people, including authority figures, who are anxious to solve, clinically or otherwise, what they see as the “problem” of her identity.

“Fear is the driving force of all those reactions,” Vega says. As far as her own identity goes, she has stated that if she were born again, she’d choose to be trans, not cisgender – and that she enjoys unsettling the kind of people who can’t cope with who she is. “It actually gives me a physical pleasure to annoy conservatives,” she smiles. “I don’t have to be violent, I don’t have to insult anyone – my mere existence shakes those people up.”

Vega herself isn’t the cautious, somewhat introverted Marina, that’s clear when you meet her; as Lelio puts it: “Daniela’s not an enigma, she’s an open book.” Even so, quite a lot of Vega fed into the development of her character; that Marina is an aspiring opera singer owes much to the fact that Vega has been singing since the age of eight.

Born in Santiago de Chile, Vega, 28, first experienced discrimination between the ages of 10 and 12, attending an all-boys school where her emerging female identity was met with brutal reactions from fellow pupils. “I faced a certain amount of violence,” she says; in Chilean interviews, she’s talked of being pushed down staircases and urinated on in the lavatories. “It taught me that I had to learn to protect myself – and it made me stronger. It could have made me step backwards with my self-discovery. Instead, it pushed me further.”

Vega had very supportive parents, who helped her through the experience of transitioning in her mid-teens; her father, Igor, has appeared by her side on TV talk shows. Two particular influences were her grandmothers. One, on her father’s side, was an opera lover who helped her discover music. “She was born blind, so sound was very important to her. She’d tell me, ‘Close your eyes and listen to the television.’ I’d say, ‘Why, if I can see?’ ‘So you can share this feeling with me.’ And I came to understand sound as an image.”

Her other grandmother offered a role model in womanhood. “She was my first diva – she’s still a big diva!” Vega laughs. “She loves jewellery, high heels, painted nails, she gets in her car and drives to the beach and wears her bikini. She’s fearless. She says exactly what comes into her head – she gave me a lot of her personality. I’d copy everything she did. We’d go out walking together and I’d try to match the sound of her heels to my trainers – I’d imagine the sound was coming from my feet.” She managed to honour both grandmothers when the “diva” remarried: Vega sang a complete Handel mass at her wedding.

Making her teenage explorations into the possibilities of female identity, Vega worked at a Santiago nightspot called Club Bizarre and experimented with a range of looks, including a period as a goth. “I was into glam – David Bowie, Annie Lennox, ‘people from here’,” she adds, slipping into English. “That style let me be a little bit more free, because my family thought it was just part of a fashion trend. “At first, I was more androgynous, like (Placebo singer) Brian Molko, then I became more and more feminine. Eventually, my family asked me, ‘Where are you heading with this – are you going this way or that way?’ ‘That way.’ ‘OK,’ they replied, ‘then we’re coming with you.’”

When I got on stage, I felt alive again

Vega has described transitioning as a happy experience in itself, but it was followed by depression, because her new identity made it hard to find work. She spent about a year in bed, she says. One thing that helped her was a course of psychoanalysis and her own reading of Freud, Jung and Lacan; she’s still considering becoming a psychoanalyst herself one day. In any case, she says: “All art is a psychoanalytic journey. If you don’t go inside yourself, if you’re incapable of cleaning the dust off a painting, you won’t see the colours.”

The other thing that helped her out of her slough was her voice. Feeling particularly low, she received a nudge from the man she calls “my best friend, who is now my brother – he’s very close, we live together, he’s an actor. Basically he insisted that I got out of bed.” He was studying theatre at university and, although Vega wasn’t enrolled as a student, she got to sit in on his courses and sing at the university. “When I got on stage, I felt alive again.”

Eventually, Vega met a writer and director who suggested that they collaborate on a stage piece about her experience of transitioning. The resulting solo show, La Mujer Mariposa, (The Butterfly Woman), ran for eight years in Santiago. She made her screen debut in 2015 in a drama called La Visita (The Visit), playing a trans woman at her father’s wake.

Working on A Fantastic Woman may have been less directly personal than Butterfly Woman, but there’s a lot of herself in it, sometimes to a painful degree. Lelio tells me that many of the hostile things people say to Marina in the film – eg that she’s a chimera or a monster – came from a list of insults that Vega told him she’d had thrown at her.

Vega in her first film, La Visita (The Visit). Photograph: Alamy

One of the most difficult scenes, Vega says, is when Marina is forced by a detective to submit to a medical examination. That was especially hard, “because it’s violence by the state”. The relation of trans people to the Chilean system – and to all traditional political systems, by extension – is central to the film. It’s noticeable that Marina carries identity papers with her former male name, Daniel – not an allusion to Daniela Vega, insists the star, whose previous name was in any case entirely different. Vega still has her birth name on her passport and ID card. “In Chile, you can’t legally change your gender identity in a straightforward way. If you want to change the name on your documents, you have to go to court.” She could easily do that, but refuses to – that would mean recognising political oppression.

One of the advantages of her new prominence, Vega says, is that she’s been able to air her political convictions in a country that is still in many ways deeply conservative, nearly 30 years after the end of the Pinochet dictatorship. Talking about her school years on Chilean TV, she said that even then, in the first decade of this century, “it was a different country – you could still smell the gunpowder”.

Vega doesn’t consider herself an activist – “I feel that art deals with issues way before any political organisation” – but she likes to speak her mind. Accepting the best actress prize at Chile’s Caleuche acting awards in January, she urged, “Rebuild this country – expand the limits of thought.” Regarding the oppression of trans people in her continent, she says: “Latin America is not that different from the rest of the world. Some of us have been trying to get from the edges into the centre, but we’re very few. The world is still very resistant to understanding the diversity of human beings.”

Meanwhile, Vega has mixed views on whether cisgender actors should be cast in trans roles. “I have two different takes. As an actress, I don’t mind if a cisgender actor plays trans. But as a trans woman, I feel that many times we weren’t allowed to show what we can do and we can do many things.” Personally, she’s keen to play not just trans roles but cisgender men and women – she’s just played the latter in a Chilean film called A Sunday in July in Santiago.

Right now, with both A Fantastic Woman and Vega garlanded with awards and nominations, the world is at her feet and it seems to belong there. When he saw her on the red carpet in Berlin last year, says Lelio, “I was so impressed – I felt she’d been preparing for this all her life”. Maza adds: “She’s fun, she’s intelligent; by the end of the evening she’s the centre of the party. Stars are made of that and she’s definitely a movie star now. She glows.”

Stardom is hard work, though. In early February, the day before Spain’s Goya awards, I catch up with Vega on the phone to find out how she’s doing in the run-up to the Oscars. Notwithstanding the distancing effects of a crackly conference call with an interpreter, she’s a lot less voluble than in London: she tersely says she’ll only talk about the film, nothing personal. You can imagine that a year on the circuit has taken it out of her, especially given that she has not just had to talk in detail about herself but also implicitly been expected to represent every trans person who hasn’t made a feted movie.

She does reveal a few things: one, that she’s been offered a contract to write a book about her experience over the last year and that she’s going to do another one-woman stage show, inspired by the Chilean poet Stella Díaz Varín. And she has a couple of surprises in store, she says. I ask whether her success has led to international offers, but she’ll only say, “That’s the thing about surprises, you have to keep them to yourself.” As for the Oscars, and whether the Academy is ready for a trans drama starring a trans actress, “the world is ready, not just the Academy”.

In any case, the following day, Vega pretty much states the essential. In Madrid, A Fantastic Woman wins the Goya award for best foreign Spanish-language film. Vega steps up on stage with the film’s team and, leaning towards the microphone, says just four words: “Rebeldía, resistencia y amor” – “Rebellion, resistance and love.”

A Fantastic Woman opens in the UK on 2 March