Last summer, Sydney Sweeney was dubbed the scariest girl on TV by The New York Times. Not for playing a violent killer or a sadistic villain, but something far scarier: a Nietzsche-reading, pool-lounging rich kid who can destroy your self-worth with just one withering look. “I love it,” she says of the dubious honour. “It’s definitely not a title I thought I would ever receive, but I’ll take it.”

The rich kid in question is Olivia Mossbacher, one of an ensemble of marvellously monstrous characters in The White Lotus. HBO’s biting wealth satire, set in an all-inclusive Hawaiian holiday resort, became a hit for its superb skewering of privilege and performative wokeness. Olivia was a college student dragged along on the trip by her wealthy parents, who spends her days sunbathing with her friend Paula, savagely judging fellow guests in between chapters of philosophical texts. Like the sharks that lurk in the nearby waters, this terrible twosome can smell their next victim a mile off. And they’ll tear them apart with glee.

Sweeney herself is nowhere near as terrifying. Down the phone from Los Angeles, the 24-year-old is energetic and giddy. Words gush out of her: gossip, opinions, anecdotes. Ask her about her dog, Tank – “he’s in the backyard staring at squirrels” – and she’ll practically combust with joy. She’s frightened of Olivia, too. “I’ve not been around many Olivias but I’ve had brief encounters with some and they’ve scared me.”

You’ll have seen Sweeney before The White Lotus, usually playing characters who feign toughness but who are actually deeply insecure. There was child bride Eden in The Handmaid’s Tale; the intense, suicidal teenager Alice in Sharp Objects; and, in teen drama Euphoria, the sensitive high-schooler Cassie, who flirtatiously removes her knickers one minute, disintegrates with anxiety in the bathroom the next. She is particularly proud of that performance – not that the critics took much notice.

“With The White Lotus, I felt like people were finally recognising the hard work I’ve been doing,” she says. “This is something that has bothered me for a while. I’m very proud of my work in Euphoria. I thought it was a great performance. But no one talks about it because I got naked. I do The White Lotus and all of a sudden critics are paying attention. People are loving me. They’re going, ‘Oh my God, what’s she doing next?’ I was like, ‘Did you not see that in Euphoria? Did you not see that in The Handmaid’s Tale?’”

She believes there’s “a stigma against actresses who get naked on screen”. “When a guy has a sex scene or shows his body, he still wins awards and gets praise. But the moment a girl does it, it’s completely different.”

In the first season of Euphoria – think Sex Education in LA, spiked with dope and OxyContin and shot in a woozy neon haze – Cassie was at the centre of a slut-shaming storyline. Left by her heroin-addict father as a child, she has spent her adolescence seeking validation from guys through sex. When boyfriends ask if they can film her, she says yes, thinking that one day, one relationship might stick. It’s not long before the videos are spread throughout her school.

In a cruel case of life imitating art, screen grabs of Cassie’s nude scenes were smeared across social media after the series aired. Sweeney only found out when her younger brother was tagged in the posts. “That was the most hurtful thing that anybody could do,” she says. “What I do is completely separate from my family. My character is completely separate to me. It’s just so disrespectful and distressing.” How does she cope with it? “I don’t think there is actually a coping mechanism to be honest. You just get used to it.”

Sweeney has never felt uncomfortable shooting Euphoria, where there’s an intimacy coordinator on set. “Sam [Levinson, the screenwriter] is amazing,” she says. In the new season, which kicked off on Sky Atlantic this month, “there are moments where Cassie was supposed to be shirtless and I would tell Sam, ‘I don’t really think that’s necessary here.’ He was like, ‘OK, we don’t need it’. I’ve never felt like Sam has pushed it on me or was trying to get a nude scene into an HBO show. When I didn’t want to do it, he didn’t make me.”

Not every project has been so smooth. “I’ve had experiences where I want to go home and scrub myself completely raw because I feel disgusting,” says Sweeney. She puts one situation down to a director not communicating properly and refusing to make changes to the script. “I didn’t feel comfortable with my cast mate or the crew, and I just didn’t feel like my character would be doing it. That made me even more self-conscious. I didn’t feel like I was able to speak up.”

At the end of Euphoria season one, Cassie had an abortion and was essentially abandoned by her boyfriend McKay. As the second season opens, she’s struggling with being single for the first time and hooks up with Nate, a violent bully who previously strangled her best friend Maddy. It doesn’t go well. Cassie falls into a depression and hits a low at a party, where she gets so drunk, she projectile-vomits in a Jacuzzi. It was horrendous to film.

“They had to design this thing for my mouth that looked like a horse bit,” she says. “It was attached to tubing that was then taped down my hair and back, and connected to a tank that they hid off camera. During the scene, the tank would get turned on and fill my mouth with the throw-up. I don’t know what it was. It did not taste or feel good. I had to look like nothing was happening and hold it in until it was time to vomit. It was so bad.”

Cassie is put through the wringer in this season. In another full-throttle scene, Sweeney was hurtled along a Santa Clarita desert road in a car rigged onto a truck. Later that episode, she practically melts with fear behind a door as Maddy, suspicious of Nate’s antics, tries to hammer it down.

Sweeney’s own teenage years couldn’t have been more different. She grew up on the border of Washington and Idaho. Her family has lived on the same lake for five generations now, in a house with no internet but plenty of bats and mice. “It’s a different way of life out there,” she says. “It’s very simple. Family is everything. I was in every single sport possible. I was on the soccer team, the baseball team, the snow slalom ski team, I was wakeboarding…”

Aged 11, Sweeney got into a terrible wakeboarding accident. “My face hit the bottom spin of the board and sliced open, next to my left eye,” she says. “I had 19 stitches. I was so terrified of getting back on my board afterwards. But the moment my stitches came out, my mom took me back to the lake, told me to get into the water with my board and would not let me out until I stood up on it.”

It was around this time that Sweeney realised she wanted to be an actor. Maybe it seemed like a safer choice than professional wakeboarding. A small, independent zombie movie came to town and she begged her parents to let her audition, putting together a business plan to convince them.

The plan worked. “I’m really thankful to my parents,” she says. “They sacrificed almost everything. They had to leave their home they’d been in for their entire lives. LA is ten times more expensive than where I grew up. All the financial stress, family stress, it had a lot of wear and tear on us and my parents ended up getting divorced. It was not a happy road to get to where I am right now but I try to give back as much as I can.”

I believe her. Sweeney is one of life’s doers. When she can fit in classes around her Euphoria filming schedule, she’s studying for her degree in business. She has also, at 24, set up her own production company, Fifty-Fifty, which focuses on adapting female-led stories. And during the pandemic, she toiled away fixing up her dream car, a bright red original 1969 Ford Bronco. She never stops, and she’s living out of a suitcase. “I kind of feel like a nomad. I’m never in one spot that long,” she says. “I love it.”

New episodes of ‘Euphoria’ season two are out every Monday on Sky Atlantic and NOW