She added: "Apparently, when she came back he said: 'What the f***? You've spelt her name wrong!'
"What were they going to do, though? Once it's on the piece of paper, it's on the piece of paper. And that's me. A spelling error."
Meanwhile, Knightley - who is known for her love of red lipstick - revealed that she follows her mother's theory that a bright colour lipstick is like an "armour".
She added to the March issue of Elle UK magazine: "Lipstick is an armour to the world. My mum had a thing when we were growing up, if she'd had a s*** day or if something had gone wrong, she'd put her red lipstick on.
"I still abide by that. If you're doing something hard, a really vibrant colour is a good thing. Lips are the easiest thing to put colour on. The nose doesn't work so well - it's a tricky look. Lips, however: quite good."
- Bang! Showbiz