She said: "I read for a different vampire, called Bree, who is a brunette with short hair that is 13 years old and completely not me, but I went for the audition just because it was a big project.
"I can tell you that I've never felt that level of nervousness in an audition room in my whole career. I had read the books, but it hadn't really sunk in what a huge phenomenon 'Twilight' was."
Despite finding everyone else in the room was completely "stressed out", the American star said she just got on with the job.
She told iesb.net: "I heard back about the audition that I was wrong for the character, but they wanted me to come back for another vampire that was essentially the same size role and everything, except she had long blonde hair, was extremely pale and was older.
"So I went in, did one audition and a week later, I got a call and then showed up on set. It was pretty rapid."