Sarah Polley rose to stardom in her native Canada as a child actress but she has never fit into the role of a typical Hollywood starlet, choosing independent films rather than big blockbusters and political activism over drink and drugs. My Life Without Me is another clever choice for the 24-year-old; a weepie about a young mother who finds out she only has two months to live which manages to be both unsentimental and moving at the same time. Spanish writer/director Isabel Coixet avoids the formulaic workings of standard Hollywood tearjerkers and studiously eschews the depressing and mawkish.

Polley’s character Ann quietly accepts the news that she has incurable cancer and decides not to tell her family. She makes up a list of all the things she wants to do before she dies which includes making tapes for her daughters’ birthdays, finding a new wife for her husband (Scott Speedman), and being nicer to her mum (an impressive performance by Debbie Harry). But there is also room on the list for more self-indulgent acts such as smoking and drinking, getting false nails and making love to another man "to see what it’s like".

Polley says: "I knew immediately I wanted to do it. I was stunned by the fact it never fell into the traps that were there for it to fall into. I never felt like it got too sentimental. There was never a moment where it weakened and we had our Terms of Endearment scene. I was waiting for it to disappoint me the whole time I read it and it never did. I was sort of surprised it could take this kind of premise and make it surprising, interesting and uplifting."

Her own mother, Diane, died two days after Polley’s eleventh birthday. Despite her own personal experiences Polley is anxious not to spout the usual clichés expected from actors about a role bringing them closer to the subject matter. "I think I’m terrified of being the kind of actor who knows more about a subject just because I made a film about it. For me the classic example is Adrian Brody saying that he knows about war because he made a film about it."

Mark Ruffalo co-stars as Lee, a troubled soul who Ann begins a tentative romance with. Polley has known Speedman, her on-screen husband, since high school. She is nothing but complimentary about her two leading men. "It’s very strange to work with two actors who are doing really well, who are really good looking and who aren’t assholes. I was constantly astonished. It set me up badly for the world in front of me because I’ve had so many disappointments since then."

Polley’s film career started when she was cast as a babysitter in Atom Egoyan’s Exotica, but it was the role of Nicole, the only survivor of a school bus crash in the director’s follow-up feature The Sweet Hereafter that catapulted the actress into the limelight, earning her awards and critical acclaim. Roles in Go, Last Night, eXistenZ, and The Claim cemented Polley’s reputation for strong performances in independent films.

She grew up surrounded by the entertainment industry. Her father Michael is an actor and her mother was a casting director. Polley remains down-to-earth and pragmatic about the profession she has been in since she was four years old. She recalls a conversation she had at a party with a successful young actor who claimed that he needed at least $2m a year to live on. Polley is incredulous at the figure and rather more realistic about her own financial needs saying: "I don’t have some out of control lifestyle that I need to support so I can do what I want and I feel very lucky."

Polley knows all about managing her own bills; she moved out of her parent’s house when she was only 14. Part of the reason she has managed to stay so grounded can be attributed to her involvement in social and political issues including local campaigns for the Ontario Coalition Against Poverty and Toronto Health Coalition. She famously lost some back teeth at a rally during a violent clash between police and protesters. Polley is currently working on the campaign for one of the candidates in Toronto’s municipal elections. He is actually leading in the polls which is proving an unnerving experience for the actress. "I’m sort of worried that he’s going to win because I think I’ve become really used to working on losing battles."

Her tendency to champion the underdog and cynicism towards Hollywood has led Polley to follow a career in small independents so it may seem odd that she has just finished filming the big budget remake of Dawn of the Dead. Up until now Polley has resisted attempts by the Hollywood system to fashion her into a star and rumour has it that she pulled out of the role that eventually went to Kate Hudson in Almost Famous. She explains: "I think that every movie should have at least one zombie in it! I’m a huge fan of George Romero films and particularly Dawn of the Dead. I had such a fun time doing it but I don’t think I’ll be making a career out of doing big Hollywood horror movies."

For now Polley is content to pursue a career which is meaningful to her instead of her bank balance. "If you have the opportunity to do things which have some meaning I don’t know why you would choose to do other things. I understand that many people don’t have that opportunity but I do right now so I’m happy to hold out for the films which have something to contribute."