‘This is all so very new,” says KiKi Layne. “We see someone who has all these new things happening to her, but then we see her start to make things happen and find her own strength and power.” She is talking about her character in If Beale Street Could Talk, but, really, she could be describing her own experience.

The film is Layne’s first, and it is hard to think of a more striking debut in recent cinema history. Directed by Moonlight’s Barry Jenkins, and adapted from a novel by James Baldwin, If Beale Street Could Talk is a story of young, black love in early-70s New York, and the obstacles it must overcome. Layne begins the story as a hesitant and delicate teenager, but grows before our eyes. Her character, Tish, falls in love with her childhood friend, a sculptor named Fonny (played by Stephan James). She loses her virginity to him and becomes pregnant, although they are not married. But then Fonny is charged with a crime he did not commit and put in prison. The couple’s blossoming love is contrasted with their harsh plight. “I hope that nobody has ever had to look at anybody they love through glass,” Tish says at one point – a line from Baldwin’s original text.

It is one of those performances that turns heads and opens doors. Young, talented and photogenic, great things are predicted for Layne. Already she has nailed down a few more roles, conquered red carpets, done the late-night chatshow circuit, featured in glossy fashion shoots and even been co-opted into the arena of celebrity gossip (more of which later). When we first meet, in London, at the end of last year, she is already settled into the role of wide-eyed debutante, which means she is attentive and on her best behaviour – and slightly reticent. She is dressed as if for a photoshoot rather than a London winter, in a cropped top and huge gold-hoop earrings. Gold rings on almost every finger accentuate her fluttering hand gestures.

Watch the trailer for If Beale Street Could Talk

She found out about the film from a friend keen to be cast as Fonny. “He asked me to be his reader as Tish for his audition tape, but when he sent me all the info I thought: ‘Why am I not auditioning for this?’” Even before she read the script, she says, Layne read the character description, “and, for whatever reason, literally the first words out of my mouth were: ‘But that’s me.’”

At that point, her career was not going well. She had moved from Chicago to Los Angeles two months earlier, she says, to attend another audition, which led to nothing. “It was really last-minute. I did not have the money to keep flying back and forth between Chicago and LA, so I just said to myself: ‘Girl, if you gonna go out there for that audition, you gonna stay.’” When she narrates herself talking to herself, she slips out of refined “interview KiKi” into a less inhibited persona, with a sing-song voice. “So I just packed up and left, which is definitely not the best way to move across the country.”

It is kind of romantic, though, I suggest.

“Yeah, until you’re there and you don’t have a home, and you’re sharing a twin-size bed with your best friend, and you don’t have a job. So it was a lot, those first couple of months, so much so that right before I submitted my tape for Beale Street, I was considering going home – and not home to Chicago but home to Cincinnati.” Cincinnati is where Layne grew up and where her parents still live.

But, of course, Layne was called to New York for a “chemistry read” with James – which sounds like an odd, panda-mating-like procedure but turned out to be more like a rehearsal. She beat 300 rivals for the role, then became a nervous wreck. “Every time they announced new cast members, I was just like: ‘How did I get into this movie?’” But Jenkins creates a supportive atmosphere, she says. The recurring adjective she uses is “warm”. “I don’t really know if that’s a conscious thing he does or that’s just his natural energy. A big part of it is how patient he is, which makes you comfortable as you try new things.”

Chemistry … Layne as Tish with Stephan James as Fonny in If Beale Street Could Talk. Photograph: Tatum Mangus/AP

The chemistry between Layne and James is palpable, but Beale Street is not a story of earth-shaking passion. Tish and Fonny’s relationship is tender and intimate, heightened by close-up camerawork, a colourful visual palette and plaintive strings on the score (and great outfits). The mood is reminiscent of a Douglas Sirk melodrama. Jenkins has also cited Wong Kar-wai’s In the Mood For Love as a reference point. Even when the couple make love for the first time, the tone is delicate and hesitant.

This type of romance is rarely expressed in modern cinema, and Tish is the type of character that is rarely written for African-American women. Her family, too, are atypically supportive and liberal and loving. Jenkins has likened his own unhappy childhood to that of his hero in Moonlight, but Layne’s was closer to that of Beale Street, she says. She was the “baby of the family”, “the odd, artistic one”. Her mother works in HR, her father is a boiler-room operator. She told her parents she wanted to perform when she was seven years old and they immediately took her to a performing arts school, then supported her through acting studies at Chicago’s DePaul University.

In Beale Street, Layne was also the baby of the family. “You see all these people coming around Tish as she’s experiencing new things, and that’s how it was. Not just the cast but the whole crew.” In particular she is thankful to Regina King, who plays her mother in the film and has been nominated for a best supporting actress Oscar. “She’s amazing all the way round. I still call her ‘Momma’.”

Beale Street’s depiction of a close-knit African-American community might seem idealistic, but it is set against a backdrop of spirit-crushing racism. Even renting an apartment is shown to be a challenge for a young black couple of the era. It is clear that Fonny’s rape charge is trumped up by a neighbourhood cop with a grudge, but hopes of proving his innocence are slim. There is little justice and every expectation of injustice. Before he is arrested, Fonny runs into an old friend, played by Atlanta’s Brian Tyree Henry. Over dinner, Henry’s character explains he has just got out of prison, having confessed to a crime he did not commit for the sake of a shorter sentence. “They can do anything they want to you in there,” he tells Fonny. “The white man is the devil.”

Baldwin was never one to mince words about racism in the US, and his diagnosis was often both piercing and eloquent. He wrote If Beale Street Could Talk towards the end of his career, in France in 1974, when his fiery passion for the civil rights movement had perhaps mellowed a little and he had come to revere African-American family life. A few years earlier, in an open letter to the activist Angela Davis, Baldwin wrote: “The American triumph – in which the American tragedy has always been implicit – was to make black people despise themselves.” Perhaps Beale Street was his antidote.

“You definitely hear Baldwin’s voice in terms of how he feels about these injustices and these issues,” says Layne. “But there’s so much love in it, which I think is what makes this story so special. It’s really about how love, and black love in particular, is so powerful in the face of all that adversity and those injustices that the black community faces.”

In that way, the story feels depressingly up to date. The cast drew inspiration from more recent victims of racial injustice, such as Kalief Browder, who spent three years at Rikers Island awaiting trial for theft, having protested his innocence and refused a plea deal. He was released without charge in 2013. Two years later, he killed himself. Jay-Z later produced a documentary series on Browder, which Layne studied closely. “I paid more attention to his family and what they were experiencing: fighting to get him out and also having to somehow move forward with your life,” says Layne. “That is part of the story that often gets overlooked, and we forget about the families that are left behind. There are real people every day in these circumstances.”

Layne as Tish: ‘You definitely hear Baldwin’s voice in terms of how he feels about these injustices.’ Photograph: Annapurna Pictures/Kobal/Rex/Shutterstock

As it happens, Layne’s next film is another touchstone of African-American literature: Native Son, by Richard Wright. The novel was written in 1940 but this new version – adapted by playwright Suzan-Lori Parks and directed by the artist Rashid Johnson – is set in the present day. Again, the issues of race and power it brings up are very much current. Layne plays Bessie, the girlfriend of the main character, Bigger (played by Moonlight’s Ashton Sanders). She is not another Tish, the actor says: “Bessie has definitely been around the block a few times.” Layne has also been in Rome making a half-hour-long film with Luca Guadagnino, co-starring Julianne Moore and dressed by Valentino.

“My friends are like: ‘How does it feel to be famous?’ And I’m like [she slips out of interview KiKi again]: “‘I am not famous. Don’t nobody know who I am. I still be living my best life, shopping at your local grocery store, picking up my apples and stuff, and just moving right along.’”

Life has been moving fast, however. When we speak again this week, Layne has just returned from Sundance, where Native Son premiered. The film, and her performance, received some praise, but equal attention was paid to Layne’s association with Black Panther star Michael B Jordan – which generated headlines such as “Michael B Jordan gets super-flirty with KiKi Layne”. “There’s nothing to say,” says Layne. “I was at a party with a couple of friends that night, so it’s just funny they picked that out.”

Two weeks ago, she also found herself a topic of discussion simply for mentioning in an interview that she was “actively plotting” to play the X-Men’s weather-controlling superhero Storm. Twitter immediately turned to Alexandra Shipp, who played Storm in the last X-Men movie, who graciously sidestepped the issue, saying: “I won’t ever badmouth a fellow actor.”

It was a lesson to Layne: “I was like: ‘Whoa. OK, that escalated quickly,’” she says. “But playing Storm is something I’ve wanted to do since I was a little girl. I’m not going to ever feel bad about sharing what my dreams are.” Who can blame her for letting the world know what she wants? It seems to have delivered for her so far. Perhaps now, rather than waiting for things to happen, Layne is ready to make things happen.

• If Beale Street Could Talk is released on 8 February