The movie's costume designer Keri Langerman spoke about crafting Portman's clothing for the role in an interview with Deadline.
According to Langerman, Portman simply asked: "Is it possible if we could just not use animal products for my costumes?" Having already worked with vegan actor Rooney Mara, the designer was fully onboard.
Langerman also revealed that after crafting animal-free costumes for Mara and Portman, she may consider changing the way she works in the future.
"It actually makes me wonder if I could do this with more, if not every project, because it is a senseless use of an animal, when you can get a cinematic, stunning movie without that," she told Deadline.
"I really admired that she had her morals, and she wanted to stick to them, but it wasn't something that she felt she needed to impose on people in an aggressive way. It just felt really natural, and when she asked, it was super easy, and we did it. I don't think it was any harder; it was just a different way of doing costumes."