Two years ago, actress Isabel Lucas packed up her Hollywood digs and came home. The ethereal Swiss-Australian beauty had just begun to make a name for herself via small, coveted roles in productions with star-studded casts: a young woman in love in the HBO miniseries The Pacific; the goddess Athena in the fantasy film Immortals; a poison-tailed decepticon with Shia LeBeouf in Transformers: Revenge of the Fallen.

With her star ascending, Lucas felt confident about calling the shots. She had a newly honed bullshit detector and had begun to detest the way she had become thick-skinned and wary in LA. She missed Australia, in particular her home town of Melbourne. And she had fallen in love.

Even now, the photos of Lucas with folk-rocker Angus Stone are beguiling. There’s Isabel and Angus in hippie threads at Californian music festival Coachella. Isabel and Angus in wetsuits aboard a catamaran, campaigning against the Japanese whale trade. Isabel, with long, golden hair, floating through an Angus Stone video clip. But what seemed a perfect pairing wasn’t to be. When Stone moved out of their Byron Bay home early last year, Lucas was left dizzy with grief.

“I came back home to move in with my partner,” says Lucas, her voice unsteady with emotion. “But it wasn’t the time for him and he maybe wasn’t ready. I guess we can’t ever make someone feel ready for all that comes with big love and long-term commitment. I went through my own process of accepting that and turning a broken heart into something beautiful.”

Indeed, Lucas has emerged from the chrysalis of heartbreak like a butterfly. The bohemian is gone and in her place there’s a bewitching, sleek screen goddess, her blonde hair cropped pixie short.

She is back in LA and she’s in demand – as an environmental spokesperson, fashion icon and red-carpet regular. She’s proving herself as an actor, too. Upcoming films include a supporting role in the crime drama Electric Slide with Chloë Sevigny and Patricia Arquette, and as the bikini-clad femme fatale Lena in the Basic Instinct-style thriller Careful What You Wish For with Nick Jonas. She also stars in Terrence Malick’s Knight of Cups opposite Christian Bale, Natalie Portman, Cate Blanchett and Antonio Banderas, due out next year.

“I was appreciative to have work as my first priority,” she says. “Work had become my second priority and that was okay. But when I came back, it made sense that work should take priority.”

Her casting in Knight of Cups marks Lucas’s first foray into serious cinema. Terrence Malick is considered one of the best directors of his generation, with credits like Badlands, The Thin Red Line and The Tree of Life. Lucas describes the experience as “enlightening”.

“It was an incredible growth opportunity, not just professionally but also on many other levels,” says the 28-year-old. “I felt so full of appreciation to be part of that project. I’ve always admired Terrence’s work, how he is an artist, how free and trusting he is, and the way he works so humbly and so in harmony with the team.”

In returning to Hollywood, Lucas has made peace with America, sort of. She tries to exist outside the consumer culture, growing her own vegies at her home in the Santa Monica Mountains and supporting local organic food producers. “I only go to LA for work and for meetings and auditions,” she admits. “But you can nurture that connection with nature wherever you live. I’m fortunate to have a vegie garden, but you can even have pots on a balcony if you live in the city.”

So passionate is the committed vegetarian about the environment that living in LA itself, with its excesses and greed, would be potentially “paralysing” for her. “It’s the thing that makes me the saddest in my life, just that lack of consciousness, the way we are going about consumerism, not having a system that appreciates sustainability and not respecting the earth. To be surrounded by a world like that can often be a trigger for me.

“But it’s like anything in life. You can choose to be dragged down by an issue or realise that there are many solutions to the problem and keep focused on that. So I have to keep my heart inspired and focus on the solutions. There are so many people in this city who are little beacons of light.”

For as long as she can remember, environmental issues have been close to Lucas’s heart. She’s the new face of a Western Australian jeweller, Linneys, and a bespoke pearl-and-diamond rose-gold pendant crafted in her honour will be auctioned to raise money for her charity of choice, the World Wide Fund for Nature, later this month. “I’ve always had a real love of pearls, anything that is a creation of Mother Nature,” Lucas says. “My mother gave me my first pearl ring for my 18th birthday, so I was really delighted to be involved.”

And though she is noted for her eclectic dress sense, much of her wardrobe is vintage or second-hand. “The environment is everything,” she says simply. “We are of the earth and when we die, we go back to the earth. There wasn’t a time when I wasn’t passionate about it.”

The daughter of an Australian commercial pilot and a Swiss schoolteacher, Lucas spent many of her formative years travelling. As a child, she lived in the Northern Territory and far north Queensland, as well as her mother’s native Switzerland, and she was nine when the family moved to live near Kakadu National Park. It was there that she befriended an Aboriginal girl who inspired her with stories of the local people’s reverence for the land.

“It was a very impressionable age and I was introduced to that way of thinking,” she says. “Taking care of the earth because it gives us our shelter, our food, our water, everything – for me it makes great sense and it was ingrained in the way I grew up.”

Over the years, Lucas has become a seasoned environmental campaigner. She is an ambassador for The Whaleman Foundation and the Sea Shepherd Conservation Society, anti-whaling groups dedicated to protecting the ocean’s fragile ecosystem. She also supports the non-profit volunteer organisation Aussie Action Abroad, and in 2007 she spent two months helping out in a village in Namibia.

Later that year she joined activist group Surfers for Cetaceans to protest against the annual dolphin hunt in the Japanese town of Taiji. The group paddled out to the dolphins but were stopped by fishing boats and had to flee the country to avoid arrest. For a time, Lucas was a wanted woman in Japan. “We were actually quite aware of the possibility of that happening,” Lucas said at the time. “We had our passports wrapped in plastic slips in our wetsuits in case the police came down and detained us.”

Despite her commitment to her career, Lucas still longs for Australia. She returns frequently to her parent’s home in the Yarra Valley, often every few months. Most recently, she was back to celebrate her sister’s birthday. “I’m aware that one day I would really love to come back home and stay home,” she says quietly.

It was under a mango tree, in the resort town of Port Douglas, that Lucas was famously discovered in 2002. Sydney talent scout Sharron Meissner, who was holidaying there, saw Lucas and asked her if she was interested in modelling. Lucas declined. What about acting? Lucas, who had already been taking drama classes, didn’t think twice.

Meissner, who heads her own company, Meissner Management, remembers her as “breathtaking”. “She looked so beautiful – natural, no make-up, flowing golden locks, a movie star if ever there was one.”

A year later Lucas auditioned for Home and Away. She missed out on that particular role but the producers were so impressed they created a part especially for her. In 2004, aged just 19, she won the Logie for Most Popular New Female Talent.

While many soap stars are eager to smudge out their humble beginnings, Lucas remains grateful to the show. “It’s such a well-oiled machine,” she says. “It really teaches young actors to be guided by their own intuition. They’ve got great drama coaches and it’s such a supportive cast. So many great actors have gone through.”

Indeed, Lucas is in good company in Hollywood. As well as the established ranks– Kidman, Blanchett, Watts and co – there’s a growing crop of fresh young Australians such as Jessica Marais (Packed to the Rafters), James Frecheville (Animal Kingdom), Firass Dirani (Underbelly), Sophie Lowe (Beautiful Kate) and Oliver Ackland (The Slap). Leading the pack is Lucas’s former boyfriend and Home and Away cast mate Chris Hemsworth, whose role in the formula one blockbuster Rush has seen him move from Thor hunk to sought-after actor.

Meissner says that these days, whenever she signs someone new, the first thing they want to do is have the “LA conversation”.

“Some go there and do well, which we hear about,” Meissner says. “But no one talks about the many who are unsuccessful and return home broke, demoralised and ultimately disappointed. Not many actors survive Hollywood – it’s really tough there. Isabel has managed to adapt, which is a huge accomplishment.”

If the gossip is to be believed, Lucas has also had many a fine romance in Hollywood. Between Chris Hemsworth and Angus Stone, there’s been Joel Edgerton, Jake Gyllenhaal and Adrian Grenier. Indeed, in the days after our interview, one website claimed that she was engaged. Lucas says she hates the attention on her private life, adding that she socialises very little outside a small circle of treasured friends, mostly fellow Australians.

“There is some kind of connection to that upbringing or mentality, so perhaps that’s why I’m subconsciously drawn to those friendships,” she says. “There’s a good Aussie contingent here but I’m really focused on work at the moment.”

She says it again, as if taking comfort in the idea. “I’m really grateful to be really focused on work.”