In Catherine Hardwicke's new film Miss You Already, Toni Collette plays a lively woman who is diagnosed with breast cancer just as her lifelong best friend, played by Drew Barrymore, is starting infertility treatment. But this certainly isn't the usual chick flick, which is what drew Collette to the role.

Drew Barrymore and Toni Collette in 'Miss You Already'Drew Barrymore and Toni Collette are firm friends after epic drama 'Miss You Already'

"When I read the script, it's so clever and witty that I got lost in it. It's almost like I had no choice," she says. "It just spoke to me in ways that I really couldn't understand at the time. I loved that it seamlessly moved between moments that were very poignant, moments that were very deeply moving and those that were hysterically funny and had me screaming with laughter. It represents the way we really exist in the world. And I loved that my character was kind of spiky - she deflects any kind of sympathy."

She had to shave her head for the role. "We did not want to misrepresent the experience at all. Everybody else was concerned about how intense it would be for me, but I would have done anything for this movie. I loved it so much."

Watch the trailer for 'Miss You Already' here:

Collette didn't really know Barrymore when they started working together, but their connection was "instant and easy," she says.

"We unzipped and jumped right in," Barrymore laughs. "We had the electric connection, and you can't fake it. You hope for it, but you don't know what it's going to be like when you show up."

More: Read our review of 'Miss You Already'

For her part, Barrymore loved the challenge of playing the kind of role she's not usually associated with. "I got to act as someone who is the definition of what respect means to me," she says. "We got to tell this messy, beautiful, amazing, honest, dark, truthful, incredible story. I feel so lucky that one day I can show this film to my daughters and say, 'Look at this story that's so representative of life.'"

More: See pictures from the TIFF premiere of 'Miss You Already'

Barrymore sees Miss You Already as a celebration of life. "You're not always perfect and weepy," she says. "You're selfish and you're angry and it's humorous and you make each other laugh - you're connected, you're distant. Lifelong friendship takes in so many extraordinary things: it's birth, it's death and that's what's all in this film somehow in the most unheavy-handed way."