With her Amazonian appearance and regal manner, meeting Sigourney Weaver is rather like interviewing a thoroughbred racehorse. With a degree from Yale.

Sipping mineral water in a swish Berlin hotel, the 56-year-old actress is bright and gracious company, but there is a hint of inner steel beneath the cordial banter. It is appropriate, perhaps, for someone who has spent much of her screen career playing maverick women in macho surroundings, from outer space to the African jungle, from boardroom battles to political coups.

In her latest film, Weaver plays another lone woman, this time adrift in inner space. Co-starring Alan Rickman and directed by Marc Evans, Snowcake is a tale of redemption set in a wintry Canadian backwater. Weaver’s remarkable performance as Linda, a recently bereaved mother who suffers from autism, is superbly rendered and often surprisingly funny.

“I’d never met a character like Linda before,” says Weaver. “I liked the fact that it included her autism but that was not the focus of her story, and neither was it necessarily the definition of who she was.”

Before shooting Snowcake, Weaver spent several months researching autism, eventually meeting several real-life role models for the character. “What I discovered was that every person with autism is different,” she says. “For as much time as I had, which was about nine months, I slowly made my way through the spectrum trying to locate the specifics for Linda. And ultimately I met two or three people whom I specifically modelled the character on.”

Snowcake may seem a left-field project for a sometime Hollywood vamp and action hero, but Weaver insists offbeat roles have always been her natural calling. “I come from off-off-Broadway in New York, so I’m more drawn to the edgier things,” she says. “Most of the stories I want to do are in the independent film world.”

Many actors make similar claims when the blockbuster offers run dry, but Weaver’s CV confirms her impressive diversity. Born Susan Weaver in New York in 1949 to a TV executive father and an English actress mother, she was passionate about drama and literature from an early age. At 14, she co-opted her name from a character in F. Scott Fitzgerald’s The Great Gatsby. After graduating from Stanford and Yale, she spent much of the 1970s appearing in off-Broadway plays.

Weaver’s film breakthrough came relatively late, earning a measly $50 for a cameo in Woody Allen’s Oscar-winner Annie Hall, in 1977. But it was enough to secure her the career-making role of Ellen Ripley in Ridley Scott’s sci-fi classic Alien. At 30 she became one of cinema’s first post-feminist action heroines.

“Alien was ahead of its time,” Weaver says. “Now it’s an accurate reflection in the sense that you see a woman being the leader and taking care of business. It’s not accurate in terms of the movies, where men still dominate in leadership roles, and audiences perhaps prefer that. But for women action heroes, there’s now an expectation that they have to look glamorous all the time, even while they’re saving the world. That’s fine, but there should be more of a range.”

Even in her superstar prime, Weaver continued to balance big studio comedies such as Ghost Busters and Working Girl with more substantial dramatic projects including Gorillas in the Mist and Death and the Maiden. Along the way she picked up three Oscar nominations, two Golden Globes and a Bafta. She also married the theatre director Jim Simpson in 1984, and gave birth to a daughter, Charlotte, in 1990. Balancing work with parenthood is not, apparently, a problem.

“My husband is wonderful at taking turns with me,” Weaver says. “That’s what we’ve tried to do since my daughter was born, actually. I’ll be full-on, then he’ll come back and I’ll be able to go away. She’s sort of used to it now.” Motherhood, Weaver says, has slightly curtailed her career ambitions. “Sometimes I feel like I should be writing or directing,” she sighs. “But I’m married to a director, so I know how hard that is. Also, if you’re a mother and you do a role, that’s about four months out of your life. If you’re directing a movie, that’s two or three years. Part of it is just laziness, and part is just feeling like I should be at home more.”

All the same, Weaver has maintained a steady output of quality acting work well into her fifties, from Ang Lee’s bleak relationship drama The Ice Storm in 1997 and Dean Parisot’s sci-fi spoof Galaxy Quest (1999) to M. Night Shyamalan’s chiller The Village in 2004. Where once she mourned the declining number of decent roles for middle- aged women, she has emphatically disproved that trend herself. “Actually, I don’t think I have made those comments,” she protests. “What I said is I think it’s hard for men to find good roles too. There are maybe more roles for men, but the quality of the role is a different thing. I actually think my roles have become more interesting as I’ve gotten older. It’s true that I haven't been in too many glamorous love stories, but I think that was more the Alien effect than the dearth of those kinds of roles.”

After Snowcake, Weaver already has a clutch of further releases on the horizon. Making its world premiere at the Venice Film Festival next month is Douglas McGrath’s Infamous, a biopic of Truman Capote, which stars Toby Jones as the fabled author alongside a glitzy cast including Weaver, Sandra Bullock, Gwyneth Paltrow and Daniel Craig. Fatefully, Infamous arrives soon after Bennett Miller’s Capote covered similar ground, earning Philip Seymour Hoffman an Oscar and a Bafta.