More at home in the bush than Hollywood, the demure Isabel Lucas can be outspoken when she has to.

Isabel Lucas is yin and yang personified. Everything about her has an all-pervasive air of opposites being perfectly balanced.

This is the surfie chick who dyed her blonde locks brown. Who shuns the limelight but dates headline-grabbing Hollywood heart-throbs such as rumoured new beau Jake Gyllenhaal.

The actress is crippled by shyness – her first Logie-winning role included a character who was virtually mute for weeks – but she is driven to speak out and even get arrested for her beliefs on animal rights and global warming.

And she’s the newly arrived Hollywood wannabe that lectures director big-shots on the carbon footprint of their private jets and knows Steven Spielberg personally as “Steve”.

Isabel Lucas is a beautiful confusion. “I’m real,” she says. “I may make mistakes but I prefer that to lying.”

At 25, she’s already a Silver Logie winner for her role in Home and Away, star of the action blockbuster Transformers: Revenge of the Fallen and the vampire flick Daybreakers, and was one of the key local stars in the Australia-based episode of US TV epic The Pacific.

She also has four more films in the pipeline, including the role of Athena, goddess of wisdom, in Immortals, now being filmed in the US and co-starring John Hurt.

Lucas is the latest in the long line of Aussie sirens to make a splash in Hollywood (and pick up a good-looking hunk along the way ).

But she had already packed in a lot of living before she was plucked from obscurity in Port Douglas markets at the age of 17 by Sydney theatrical agent Sharron Meissner.

The daughter of a Swiss-born dance therapist and Australian pilot father, Lucas’s early years were spent in Melbourne, either side of a spell at school in Switzerland, before moving to remote Kakadu National Park, then going to school in Cairns.

Living with raw nature on her doorstep, the seeds of spiritualism – and a determination to speak out on injustice and cruelty – were sown.

“When you’re 10 years old, you’re at an impressionable age and a lot of life lessons are subconscious,” she recalls. “Kakadu was a unique experience and I think that’s where I developed a very real connection to nature.”

An incident where a local youngster tortured a frog to death in front of her still haunts vegetarian Lucas years later.

“I was shocked and upset with myself for not saying anything,” she admits. “I felt so guilty and furious afterwards.

“From then on, I thought if anything like that happens again, I’m going to say something. I’m grateful to him for that experience – that’s how you learn, through your mistakes.”

With Meissner as her mentor, Lucas took acting classes and so impressed television bosses, the role of Tasha Andrews in Home and Away was written for her.

But the lonely move to Sydney left her literally dumbstruck on screen, with the new character kept silent for weeks as Lucas adapted to her new life in front of the cameras.

“The cast was welcoming but I was not confident about being in front of a lot of people,” she says. “It encouraged me to come out of my shell and trust myself and that everything was going to be OK.”

After three years she quit the show and went travelling, determined to find more to life.

“There’s so much that’s not important – the photos, what you wear on the red carpet and so much pressure to come across the right way,” she says.

On returning from her travels, she signed up at the Victorian College of Arts but was almost immediately snapped up by Steven Spielberg for The Pacific before moving to Hollywood.

“Los Angeles is a mad town,” she admits. “I’m kind of in denial about living there. It’s a funny place, an odd environment to live in … but I’ve decided to like it.

“With acting, there is quite a superficial side where it is based around money and wanting to succeed and fame, and that’s OK.

“But there is another side, which is about knowledge and storytelling. It is about creatively exploring characters and different concepts, ideas and stories. That’s the part I’m attracted to.”

Since moving to Tinseltown barely two years ago, she’s dated Entourage star Adrian Grenier, been in a car crash with Transformers co-star (and “platonic friend”) Shia LaBeouf and has been in Montreal this month with Brokeback Mountain star Gyllenhaal to help him, ahem, get over his split with Reese Witherspoon.

On the activism front, Lucas has been arrested by Japanese authorities for protesting against the slaughter of whales and dolphins (and then had to return to Japan for the world premiere of Transformers, despite an outstanding arrest warrant) and climbed Mount Kilimanjaro to raise awareness about clean drinking water.

But despite these experiences, an awkward appearance on Rove last year revealed her still to be the shy bush girl who’d rather be diving into an outback billabong.

“It’s very scary – sure I get nervous doing press,” she admitted at the time. “I’ve had no experience of doing junkets or big premieres before. This is all new to me.”

But she accepts the reality of her life and hopes to use it to get her conservation messages across to the masses.

“It’s something I know I will be faced with more now and hopefully I can learn to deal with it graciously,” she says. “I stay very separate from all the buzz and hype – I don’t go out a lot.

“But I do feel I am in a unique position where I can use my public status to draw attention to things that matter to me and hopefully a lot of other people as well.”

Though she also admits: “I don’t want to push my ideas on other people. Everyone should think for themselves.”

She remains a balanced kaleidoscope of contrasts, which only adds to her allure.