In the upcoming fictionalized film, de Armas, 34, plays the famous Hollywood actress, who died 60 years ago at the age of 36. De Armas told AnOther magazine that over the course of Blonde's production, she watched some of Monroe's movies "hundreds of times."
"[Director] Andrew [Dominik] had two monitors, the real Marilyn in the scene and me. And everything, every angle, had to be exactly the same. So that was me watching these films hundreds and hundreds of times," she said of pulling off the uncanny recreations.
De Armas also admitted that she "experienced a lot of fear and insecurity" on set during the making of the film — and she was instructed to channel those feelings into her Monroe performance.
"I felt in a very vulnerable position. Not just in specific difficult scenes; the whole process was overwhelming for me," said de Armas. "Most of the time I thought I was doing it wrong. I was thinking, 'What are these American actors thinking of me? They know this person better than me, they've grown up with her. What are they thinking about my accent?' "
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"Andrew could sense that discomfort and right away he told me, 'That's how she felt. Embrace it,' " she continued. "She was feeling insecure and unprepared and judged and undervalued all the time. So I had to trust my emotions were adding to the layers."
While she looks back at the making of Blonde as "so much fun," de Armas explained that "emotionally," the "weight of it stayed with me for sure."
"There was no way to unplug because I'd get home and study for the next day and then Andrew was on the phone until midnight," she recalled. "I would go to sleep and dream I had long conversations with her.... I don't want it to seem like I'm saying, 'Marilyn and I were connected' — not at all. But I was thinking of her so much, some days I would go home and have dinner and as I was washing the dishes I would just start sobbing, crying and crying, because I had this terrible feeling: I knew I couldn't fix it."
Blonde debuts on Netflix Sept. 28.