The last time I spoke to Jessie Buckley about her role in a film called Beast, I told her she was going to be a star. Now, just a year on, Buckley is about to go full-on supernova.

The Kerry-born actress is receiving rave reviews worldwide for her role in Wild Rose, Tom Harper’s musical fable, which sees Buckley play Rose Lynn, a wild, brash, drink-swilling, fight-starting singer with a big voice – and a big dream to match. Never seen without her white cowboy boots and fringed jacket, she is determined to become a country singer in Nashville – but that life seems a million miles away from her existence in Glasgow, where she has a criminal record to deal with and two young children.

Torn between the life she has and the life she dreams of, Rose Lynn feels trapped – and rebels through self-destruction. Failing to commit fully to either her dream or her family, she alternately inspires and frustrates the people around her. These include her mother (Julie Walters) and her boss and biggest champion, Susannah (Sophie Okonedo).

Buckley is a force to be reckoned with. Charming and charismatic, vulnerable and enraging, her performance is incredible. And that’s even before she sings. Her voice is phenomenal, and she imbues Rose Lynn’s beloved country music with a power and emotion that will instantly convert anyone who hasn’t embraced the genre before.

It’s an ideal role for Buckley, who jumped at the chance to not only play a character who loved to sing, but who is complex and bold, while also being vulnerable.

“I just bloody loved her – I still love her, she’s very hard to shake off.”

As long as we’re talking about her fearlessness – not, you know, the prison stint, or penchant for starting scraps with people down the pub, right?

Buckley lets out her trademark roar of laughter.

“Yeah, any type of bad behaviour, I now just blame her! It’s not me!”

Jokes aside, Buckley loved the character on the page, and fights against the idea that she’s “unlikeable” – the now ubiquitous adjective thrown at complicated female characters onscreen.

“I don’t think you can really read a character and say, ‘Oh she’s horrible’ – you have to read them and try understand,” Buckley says. “And the moments where people find characters crunchy or uncomfortable – who in the world doesn’t have moments in their life where they are, too? Who hasn’t wanted something for themselves and are struggling with it? And I don’t think there are many female characters who are front and centre like that, where the complexities of being a mother and wanting something more for yourself are addressed. That dilemma costs her, even in the moments where it looks like she is boundlessly, defencelessly breaking down everything around her. So I wanted to explore that. Those are the foibles that make people really human. If every character is sheened and perfect and always admirable – what’s the point?”

The film does brilliantly, though non-didactically, address the pull many women feel between their familial responsibilities and their own desires. While Rose Lynn struggles with the guilt of wanting something more from life, the father of her children isn’t present or even mentioned – a subtle yet damning indictment of how women can still be expected to sacrifice their hopes and dreams for their families. But the film also tackles discontent and ambition and passion, and the tension between wanting to do the safe thing or take a gamble on your dream.

“To actually want something for yourself is really difficult for a lot of people,” observes Buckley. “And there are paths that you can choose, paths that exist that will let you coast along, and that’s fine. But when you have a burning passion for something or you fall in love with a person, or an idea, or a dream, it’s hard. Because the moment you engage with that pull, you feel you belong somewhere else, to something else. And if your identity is pulled towards something else – it’s scary. It’s really scary. Because you’re in need of something else – and choosing that over what you have is scary and might mean leaving a lot behind.”

One of many brilliant yet devastating moments in the film is when Rose-Lynn’s mother tells her to give up her pipe-dream of becoming a famous singer, pointing to all the X-Factor style reality shows filled with young, hopeful talented people and saying dismissively, “A lot of people can sing.” It’s a layered moment for Buckley, who herself got her break when she came second in BBC’s 2008 Oliver!-themed talent show I’d Do Anything. Did anyone try to dissuade her from following her dream?

“Loads of people have said things to me,” Buckley says wryly. “And in the moment, it’s crushing. Because you question every bit of belief you have in yourself in that moment. But I think I’ve taken any negative comments and said, ‘Thanks very much, actually. Because now you’ve lit a fire under me – I want to show you that you’re wrong.’”

And she has. Buckley’s career is already notable for its thrilling unpredictability. She toured the UK as a jazz singer, before coming back to drama to play Perdita in Kenneth Branagh’s The Winter’s Tale. She then went on to play a fiery Shakespearean actress Lorna Bow in the grungy 19th century thriller Taboo, opposite Tom Hardy, before landing her breakout role in BBC’s War and Peace last year, where she won acclaim for her portrayal of the devout, fragile Marya Bolkonskaya. But to offset any public image of being a delicate wallflower, Buckley also played an enigmatic and intriguing young woman in Michael Pearce’s wickedly tense psychosexual thriller Beast. The actress seems to thrive on subverting expectations and rising to challenges.

Not that she’s always completely sure of herself. She speaks openly about experiencing panic attacks on set, and the cycle of worry that can accompany them.

“They’re funny things – they kind of creep up on you. It’s tiredness, it’s emotion, it’s risk, it’s being away from loved ones. You’ve very vulnerable, and there’s always an unknown. And acting, you’re drawn to the unknown because it’s a challenge – but you’re also scared of falling off the edge of the cliff, and you don’t know what’s on the other side. So I get them, but I also get out of them.”

Luckily for Buckley, Wild Rose reunited her with her War and Peace director Tom Harper, who she now considers a close friend, and who she credits with being an emotional rock during her moments of anxiety.

“When we were shooting the film, it was a scary thing because I really loved it and loved her, and I was getting ferocious panic attacks in the middle of the shoot,” she says. “But the joy of working with someone like Tom and having a trust and friendship like that means that whenever I’d have a struggle or a panic, he would hold it but also say ‘This is very human, and let’s explore it. Where is this actually coming from, is it coming from you or the character, can we channel it? It’s an emotion, and it’s real, so let’s let it be seen.’ And when you’re in the hands of a director, those moments can be incredibly vulnerable and you can be under time pressure to get a shot. There can be a sense of ‘Cop on, we don’t have time for this, get on with it’ – but Tom is never like that. He’s a friend first, then a director, but also manages to combine both to help me as a person and an actress.”

And, Buckley adds, Rose Lynn taught her to have a more confidence, too. Buckley isn’t a method actor and doesn’t feel the need to stay in character when the cameras aren’t rolling, but she does commit to empathising deeply with her characters and allowing their perspective into her own life.

“It’s an amazing experience, getting to be someone else for a while,” she says. “The way you look at the world is different, the way you relate to it is different. It’s like if you’re reading a book and suddenly you’re asking your friends about something you’ve never spoken about before, and their ideas build even more on your understanding. That’s the fun part. You grow with these characters. Each character who has come into my life has changed the way I look at the world. People ask me ‘How do you shake the character off’ – I don’t want to. They all help me grow.”

And another very welcome thing that Rose Lynn introduced Buckley to was country music, which the actress fell in love with on set, embracing the genre that Rose Lynn describes as “three chords and the truth.”

“Before this, I thought country was a bit, kind of hick?” says Buckley. “But I hadn’t really heard the real stuff, it was all the crap, poppy misogynistic stuff I had heard peripherally growing up. But Nicole Taylor and Neil McCaul just have an incredible knowledge of country music. It’s the stories and the characters in the songs that really got me. The song ‘Angel From Montgomery’ by John Prine is all about an old woman sitting in her kitchen, thinking back over all the things she didn’t do in her life. It’s so simple, lyrically, but the stories and the emotion and the humanity and honesty behind it are incredible. You go on a journey with these characters. It’s changed me, listening to and performing this music. Because you have to get out of your own way and let the characters take over.”

Wild Rose has been getting rave reviews for its emotional, heart-swelling storytelling and Buckley’s star-making performance. But true to form, Buckley isn’t waiting for the external validation or sitting on her laurels hoping opportunities fall into her lap – she’s already working on some projects that are challenging and inspiring her. This includes Chernobyl, the five-part Sky Atlantic mini-series that also stars Barry Keoghan.

“Chernobyl was my favourite thing I shot last year,” enthuses Buckley. “The script was insanely brilliant and honest and provocative. It was scary to take on, because these are real people, I play Lyudmilla Ignatenko, a real woman who is still alive. Her husband was one of the first firefighters into Chernobyl after the explosion. So she is kind of the civilian’s eyes and shows this journey of loss and dangerous love and grief and survival. It was an amazing feeling on set. Everyone was really committed on set, in a bold way and an emotional way. Even the extras.

“We were shooting one scene set in a graveyard and there was a Lithuanian woman in her seventies standing beside me, bawling her eyes out. And when the scene ended, I said ‘Thanks for committing’, you know? And she just held her heart and said ‘My son, my son.’ You’re literally on set with people who have experienced this. Because Chernobyl isn’t something that happened, it’s still happening. Adi Roche has been so generous with research and help with me, and we’ve become good friends. But the work she is doing is never-ending.”

Buckley will also be appearing in a biopic of Judy Garland, where she plays Rosalyn Wilder, the production assistant who worked with Wizard Of Oz star Garland during her last performances in London in the winter of 1968.

“I grew up with Judy Garland, she’s my first experience of looking at someone and thinking ‘Wow, you can actually do that? For a job?’” says Buckley. “And Renee Zellweger who plays her is, for me, one of the most amazing performances I’ve ever seen. I haven’t actually seen it, but I just hope I am giving Renee and the film as much as I got from that experience.”

As for her heroes, Buckley says she admires many people in Hollywood and the incredible, multi-faceted careers that they have carved out for themselves – actors and filmmakers such as Olivia Coleman, Frances McDormand and Charlie Kaufman. But when it comes to her own career, Buckley is determined to blaze her own trail.

“I want to figure out what I want to say to the world. Everyone’s path is different and I don’t want to copy anyone. I want to do my own thing.”