Michelle Williams has undergone a physical transformation for her new film, My Week With Marilyn, in which she plays the famously buxom Marilyn Monroe. In real life, Williams, 31, has undergone an inner transformation with regard to the death of Heath Ledger, her ex-husband and father of their daughter, Matilda, 5.

Ledger's accidental overdose from prescription medication in January 2008 left the world stunned at the sudden death of the star, only 28 at the time. For Williams, it left her feeling incredulous about the existence of anything. "For a really long time, I couldn’t stop touching people’s faces. I was like, ‘Look at you! You move! You’re here!’ It all just seemed so fleeting, and I wanted to hold on to it," she told Vogue.

Now, more than three years after Ledger's death, Williams says the tragedy has had a strange effect on nearly every facet of her life. "It’s changed how I see the world and how I interact on a daily basis," she said. "It’s changed the parent I am. It’s changed the friend I am. It’s changed the kind of work that I really want to do. It’s become the lens through which I see life — that it’s all impermanent."

My Week With Marylin, due out in November, follows the tense interactions between Monroe and Sir Laurence Olivier (Kenneth Branagh) on the set of the 1957 film The Prince and the Showgirl. Williams said she tried to gain weight to exchange her thin frame for Monroe's curves, but that all the weight went to her face. She wears padding in the film, instead.