The 32-year-old actress plays the 'Lord of the Rings' stars' wife in the crime thriller, and she's admitted that while they were shooting for a scene in the film, she was injured so badly that she still has the scars.
Speaking at the film's press conference at London's Corinthia hotel, she revealed to BANG Showbiz: "I remember that day [of filming] because Viggo is holding my body and he's grieving and he had to have a lighter on to illuminate what was happening in the scene and he's holding my body and laying me back down and I'm being burnt.
"I didn't want to say anything though, because I didn't want to ruin the scene, I was taking one for the team!"
The 'Melancholia' star revealed that the film's director, writer and film-maker Hossein Amini, didn't originally intend on giving her the part of Mortensen's character Chester MacFarland's younger wife, but she believes she brings more credibility to the role.
She said: "At first I know he [Amini] was thinking about maybe casting someone a little younger than me, to have that innocence maybe, or the flightiness of a woman who marries rich, but really what was more interesting was creating a real dynamic between us.
"A real husband and wife, and yes she's disillusioned a bit by the money and the glamour but I think that Colette truly loves Chester, and in order to make this dynamic more interesting we needed to have a more filled out woman rather than just a girl in the film."