There are so many things you don’t have control over in life. how to be able to change your body—there’s something thrilling about that.

She relates to her character’s sense of precision in particular in The 355. “I think I innately strive to do things well and properly and follow through. And when I was younger, I was certainly very guarded; I think that’s part of our [German] culture.” Kinberg, who directed her in the film, was struck by her meticulousness. “There’s a centerpiece fight between Diane and Jessica, and the two of them really wanted to do the fight themselves, without relying on fight doubles. So they worked overtime, after wrap and on weekends—to get the moves down.” To prepare, Diane added boxing and running to her routine (“I really hate running,” she says, “I like to walk—I live in New York. We walk everywhere”). Then, five weeks before filming started, Diane arrived in London, where she embarked on daily two-hour training sessions. Some days it was fight training, in which she cultivated her hitting power with boxing drills and kicks, as well as practice in wrestling, grappling, and basic gymnastics. In other sessions, she did military drills, during which she and her costars moved with various weapons through a house constructed from empty cardboard boxes. In the past, Diane had expressed a desire to work with more female coleads, something this project, written by Theresa Rebeck, offered. “It felt great to work with girls, and there was no weirdness on-set,” Diane says. “Jessica made sure all of the actresses were paid the same; we all own a piece of the movie. Regardless of how the film does, it was one of the most complete experiences. Being able to be heard and valued is so important—not just in what I do, but everywhere.” She was also heard as a mother, a title she was still figuring out while returning to her career on a set surrounded by working moms. “One thing that was wonderful about this film was that many of us were mothers. We were allowed to bring our children to set and had a trailer for the kids. That was a lovely thing, where you can sense that the producer is a woman with a child.” That setup created a blueprint for how Diane now considers potential roles. “Everything changed with motherhood—it’s such a cliché, but it’s true. The way I look at work is different. I love to work; in fact, I cherish it more today than I did before, but at the same time, you look at everything from a different angle. It’s not: What’s it going to do for my career? It’s more about: Could it fit into my schedule? How can I make it work? Is it going to be worthwhile?” Now, she takes her daughter, who is 3, with her to jobs around the world, tackling all of the associated logistics (if you’re ever looking for Montessori preschools in Warsaw, Poland, Diane’s your girl). That Reedus shoots The Walking Dead series in Atlanta adds another wrinkle. “That’s always been very hard, and probably a reason I work less,” she says. “Things just change when you have a family. You want to keep everyone together.” Recently, as her daughter becomes a full-fledged toddler, Diane has been rethinking how she takes care of herself. She sometimes feels imbalanced and realizes she’s been clenching her jaw. “I always feel tense, like I’m forgetting 5,000 things a day. I often feel like I don’t take enough time to stop for a second and take care of me, so I’m trying to get better about that.” When she can, she gets a massage or a foot rub. After she became a mother, there was also a period when no matter how much she (hypothetically) slept, she “always looked tired.” So she started taking vegan multivitamins, which she says help her feel less depleted.