It’s not every day that costume designers get to create Cinderella’s iconic ballgown, but Ellen Mirojnick has had the honor of doing it twice.

Mirojnick was on board the 1997 “Cinderella” starring Brandy, and she got to work her magic again for the 2021 feature version starring Camila Cabello. This time around, the fairy tale gets an empowering update as Cabello’s character Ella, an aspiring designer, spends her time drawing dresses and dreams of building a fashion empire.

“The film was going to be called ‘Rebel Dreamer,’” Mirojnick reveals. She kept the idea that Ella was a rebellious spirit, fiercely independent and someone who wanted to break glass ceilings. “What was important to me was how to create this mix of time — to make it timeless and not period-specific.” That translated into putting contemporary touches on a wardrobe of timeless storybook looks.

Mirojnick describes Ella’s everyday work dress,...