The British actress has always hated the way Hollywood's witches are portrayed as dark-skinned, crooked women and she wanted to give the genre a new look.
She explains, "I've been exposed to the stereotype of witchiness, which hasn't necessarily frightened me. It's all that cackling, screaming and shouting.
"What children are most frightened of is the kind of unemotional, unpredictability and coldness; the idea that somebody might switch at any moment.
"Disney has now given us a new kind of villain and I'm happy to have been a part of it. In my mind, there has been a dishonourable tradition in Hollywood of giving children the idea that villains have to be dark.
"I didn't think it was responsible, at the moment, for a globally-available American film to be making the epitome of all evil look either like a Jew or an Arab.
"Also, the children are second world war children and their father is away fighting Nazis. I thought it was important, since she is the epitome of all evil and the ultimate white supremacist, that my witch looked Aryan. I thought it was interesting to give the world a really super white villain for a change."