The first time most of us saw Saoirse Ronan was in Joe Wright's British period war drama"Atonement," as the little girl who gets her sexy older sister (Keira Knightley) into a heap of trouble. It's been seven years since Ronan earned her first Oscar nomination. Since then she played a trained assassin in Wright's "Hanna," and acted for directors Peter Jackson ("The Lovely Bones"), Gillian Armstrong ("Death Defying Acts"), Peter Weir ("The Way Back"), Kevin Macdonald ("How I Live Now") and Wes Anderson ("The Grand Budapest Hotel").

When she returns to the Academy Awards for "Brooklyn," which earned three Oscar nominations, she'll be a young woman.

Brooklyn

In a way the movie version of Colm Tóibín's book "Brooklyn," nurtured for years by writer Nick Hornby, has been waiting for Ronan to grow up. She's now 21. When we talked about her growth as an actress, Ronan admitted that she has gained confidence—from surfing the improvisations of Ryan Gosling's "Lost River" to falling in love with two very different men (Emory Cohen and Domnhall Gleeson) in "Brooklyn."

How naive was I to assume she was using her own Irish accent as Eilis, who after all is a country girl who moves to Brooklyn, while Ronan is a sophisticated urban Dublin girl who experienced the homesickness, loneliness and excitement of being a new emigre when she moved alone to New York.

Brooklyn
"Brooklyn"

Next up: She's playing Nina in a new film version of "The Seagull" and stars opposite Ben Whishaw, Sophie Okenado, and Ciaran Hinds on the Broadway revival of Arthur Miller's "The Crucible."

WATCH: "'Brooklyn' Writer, Oscar Contender Nick Hornby on Penning a Swooning, Old-Fashioned Romance"