The Toronto Star has a new article with Emily in which she discusses her new movie, Your Sister’s Sister.

Writer-director Lynn Shelton’s comedy Your Sister’s Sister reveals something you’ve probably never seen in a fiction film: genuine surprise.

Actress Emily Blunt gulps, gasps and breaks into a furious blush when Rosemarie DeWitt, playing her stepsister, reveals an embarrassingly intimate secret at the dinner table in director Lynn Shelton’s largely unscripted Your Sister’s Sister. The comedy, which was a hit with its world-premiere audience at TIFF last September, arrives in theatres Friday.

“I cried with laughter,” said Blunt, adding she told Shelton, “‘You are never getting that on camera!’ I was so mortified.”

“She (Rosemarie) sprang it all on us,” Shelton said. “It was something that happened to a friend of hers and she never forgot.”

Shelton and two of the film’s three leads, Blunt and Mark Duplass — who both seem to be everywhere onscreen these days — shared the story with the Star at TIFF the day after Your Sister’s Sister premiered.

Shelton, who first directed Duplass in the also largely unscripted Humpday, lets her three characters loose at a secluded cabin in Your Sister’s Sister. Duplass and Blunt play best friends Jack and Iris. Jack’s planned retreat at Iris’ family cottage to help mourn his late brother isn’t so secluded when he finds Iris’ half-sister Hannah (DeWitt) has already arrived to heal her broken heart with the help of a bottle of tequila. When Iris suddenly shows up the following morning, things get very complicated.

The movie began with an eight-month process to work out back stories, followed by a 70-page “scriptment,” said Shelton. This outline of who says and does what helps guide actors through the story.

“Some scenes were completely written and they (the actors) were able to pick and choose if they wanted to use the page,” Shelton explained. “Other scenes were mapped out but there was no dialogue. I said, ‘This is the emotional turn that needs to take place,’ and then it’s a matter of writing it and seeing how are we going to get to these places.”

Shelton worked with two cameras and let her actors decide what to say to each other to move the story along.

“She captures everything so you can go back where you started from,” said Blunt. “There’s never any pressure to re-improvise improv because that’s the most crummy thing to do.”

Duplass, one of the founders of the mumblecore style of low-budget, lightly scripted films with writer-director brother Jay Duplass, said he had a ball working in this “estrogen-laden world.”

“It is the greatest,” he told Shelton. “You just put me in a love triangle sandwich. My household is my wife and my 3-year-old daughter (a second daughter was born in May) and it is the greatest thing in the world and it’s no secret as a North American male, I have a high level of estrogen running through me already.”

Blunt and DeWitt met the day before shooting but had spent time on the phone and emailing to form an “accelerated friendship,” as Blunt described it. Soon they were able to communicate with the kind of sister shorthand siblings have, snuggling up in bed together to whisper secrets.

“I felt I had a really nice chemistry with her and it was easy sharing the same bed and talking into the night, which is exactly the kind of thing I used to do with my sisters.”

Shelton said the almost-documentary feel of the movie is deliberate and much of it was honestly earned, added Blunt.

“He (Duplass) didn’t know what I was going to say and I didn’t know what he was going to say. I remember having butterflies in my stomach for real. You are constantly in the moment.”