The 27-year-old stars in the adaptation of Tolstoy's classic along side Jude Law, reported Contactmusic.
"It is deeply, deeply risky. There's no two ways about it. I think some people will go and see this and absolutely hate it and want something different. But I think people will also go 'wow' because certainly there aren't films being made like this right now," she said.
"The Pirates of The Caribbean" actor was also frightened at the idea of playing a literary giant.
"Playing Anna was absolutely terrifying, because it is a role that has been played so many times and exercises a fascination over so many people," she added.
The film has been adapted by Tom Stoppard and directed by Joe Wright.