Swaying in a pistachio-green embroidered Dior gown, her hair sprayed egg-yolk yellow, and her dark eyes flashing, the actress Anya Taylor-Joy brings to mind a punk version of Hamlet’s Ophelia—just before her tragic watery end.

Bella! Divina!” cheers the photographer Paolo Roversi, as Taylor-Joy’s ethereal image appears on the digital screen. The gown, from Maria Grazia Chiuri’s debut couture collection for the French house, is one of many that the 20-year-old will don over the course of the next few hours, slipping effortlessly in and out of them, much the way she does the characters she embodies.

“This is playtime,” she says as she glides among the racks in between shots. “I can morph from one person to another really quickly. I have to think about what I can convey in a single picture.”

Taylor-Joy studied ballet but had no formal drama training; with her taut physique and unconventional beauty, she exudes the magnetic power of a silent movie star. “Look at those eyes!” exclaims Roversi moments later, as Taylor-Joy does her best Marilyn Monroe, singing “Diamonds Are a Girl’s Best Friend” while posing in a Chanel silver-sequined column topped with a cloud of tulle. “I love how ambiguous they are.”

Taylor-Joy’s otherworldliness is especially beguiling onscreen. In 2015’s The Witch, she played a tormented teenager in 17th-century New England whose family is torn apart after one of her brothers disappears. She followed that up with Morgan, appearing as a mesmerizingly violent cyborg struggling to come to terms with her human side. And in Split, M. Night Shyamalan’s disturbing thriller about a girl abducted by a man with multiple personalities, Taylor-Joy conveyed with simmering intensity not just the terror of being held captive but also the strength of mind needed to escape.

“Casey taught me to value being quiet,” she says of her character in the film. “A lot of the acting was based on stage direction rather than dialogue, so I really discovered how much I could communicate with my face.” Casey, she adds, “is an outsider with a deep internal wall. She stores information.”

Anya Taylor-Joy Is a Real Scaredy-Cat, Especially When It Comes to Revolving Doors

Up next is Thoroughbred, playwright Cory Finley’s first feature film, which premiered to great acclaim at the Sundance Film Festival in January. Taylor-Joy is Lily, a girl of much privilege and few morals who teams up with a friend to lure an outcast into killing her stepfather. “Lily is a toxic character, but more by nurture than nature—she has been warped that way,” says Taylor-Joy, almost apologetically, as she wraps herself in a white terrycloth robe and tucks into her lunch of salad and focaccia. “The biggest challenge is playing an awful human being and keeping the audience on your side despite that.”

Finley was impressed by Taylor-Joy’s maturity. “With Thoroughbred, we were trying to walk a very narrow tonal line, and to make a film that was both an honest portrait of two characters and a satirical black comedy,” he says. “So much of the film rides on Anya’s role. She had to be sympathetic and frightening, sometimes at the same time. The role was physically and emotionally demanding, and she was able to go to dark places but to snap out of them quickly.”

One easily senses how deeply Taylor-Joy is able to delve into the psyches of the emotionally complex women she has taken on in her short career. “She’s pure and open internally, and that’s why she’s riveting,” says Shyamalan. “The thing she wants to do more than anything is protect her characters. Filming Split, I would say, ‘You have to defend Casey more,’ and she would tear up.” Taylor-Joy describes herself as “very porous” to the personalities of other people, both real and fictional, and recalls how, as a child, she was just as happy hanging out with her real friends as with imaginary ones. “I would go off into the woods and play out seven different characters. I think I was purging emotions, and by putting them into a story, I felt lighter. I do feel things so intensely.” Off camera, though, Taylor-Joy is upbeat and effervescent; she can go from a posh English accent to Eliza Doolittle cockney to a Valley girl drawl in seconds.

The youngest of six siblings, Taylor-Joy had a peripatetic upbringing—her Argentinean-Scottish father was a powerboat racer, and her English-Spanish mother worked in photography and design. She was born in Miami and spent her early childhood in Buenos Aires; the family moved to London when she was 6. Nowadays, she shuttles between London and New York, and says that the itinerant life has always suited her just fine. “My mother has a video of me at age 7 declaring, ‘I’m going to be an actor,’ ” ­Taylor-Joy says with a smile. “She asks me, ‘Are you going to drama school?’ and I reply that I’m going to be in the right place at the right time. Thank God it happened.”

Indeed, she was hanging out in Central London when Sarah Doukas (who discovered, among others, Kate Moss) spotted her and promptly signed her to her modeling agency, Storm. Taylor-Joy dropped out of school at age 16 and, while on a photo shoot, met the Irish actor Allen Leech (aka Tom Branson, the chauffeur on Downton Abbey); after hearing her deliver an impromptu reading from the Seamus Heaney book she was carrying, Leech introduced her to his agent. Within four years, she was nominated for a BAFTA Rising Star Award, the British equivalent of the Oscars, and named Breakthrough Actor at the Gotham Independent Film Awards.

Back at the W shoot, three assistants are holding Taylor-Joy aloft as she slowly disappears into a frothy sea of ­Giambattista Valli lime-green silk tulle. Suddenly, she stiffens her upper body and assumes a slightly mad, intoxicated expression. The entire studio is transfixed. “I go into a meditative state in front the camera, and I feel I’m speaking to it,” she explains later. “That might sound strange. I’m always surprised by how many close-ups there are of me after filming. I’m not aware of the lens.”

I venture that it’s clear she knows a thing or two about the transformative power of clothes. “Growing up, I was a real tomboy, and I was not aware of fashion,” Taylor-Joy says. “I wore my brothers’ clothes and whatever my mom bought me. I rarely looked in the mirror.” Modeling, and acting, changed all that. “When I had my first fitting, it frightened me because I felt so unlike me. I didn’t know how to wrap myself around the idea of looking beautiful. Now, I relish the idea of getting dressed up.” She pauses, recalling a certain featherlight Valentino chiffon confection that she had slipped out of moments before. “Wearing an incandescent dress feels peaceful, like magic,” she says, before adding, unnecessarily, “I’ve always loved make-believe.”