The Atonement star, who was brought up in County Carlow in Ireland, has previously shown off her flair for accents by playing American and British characters.
Now the 18 year old will get a chance to use her natural speaking voice after being cast as the leading lady in Anderson's upcoming film The Grand Budapest Hotel.
She says: "I'm doing an Irish accent for my character. Wes just decided to let me, and I'm really chuffed. It's actually the first time I've ever used an Irish accent in a film."
The Grand Budapest Hotel, which is due for release next year, boasts a star-studded cast including Bill Murray, Jude Law, Edward Norton, Adrien Brody, Owen Wilson, Tilda Swinton and Willem Dafoe.