When Theron saw the superheroine's skimpy crime-fighting outfit of a bikini, thigh-high boots and shoulder pads, she decided to add trousers to the outfit.
The 29-year-old star admits: "When you're playing with aspects of sexuality, certain things have to be hidden. That's what my mother always used to tell me.
"I wanted to stay as true as possible to the original character, but didn't feel the need to go as far with the costume."
The sci-fi movie, based on the comic book adaptation, is due to be released in the autumn.