Irish writer Oscar Wilde maintained that life imitates art. For Oscar-nominated Irish actress Saoirse Ronan, it is the other way around - her art imitates her life.

The 21-year-old is among the nominees for Best Actress at the Oscars this year, thanks to her performance in the period drama Brooklyn.

Like her character in the movie, a young Irish woman called Eilis who emigrates to New York in the 1950s, Ronan understands homesickness all too well.

"About a year passed from the time I signed on to when we shot the film," says the actress of the film which is nominated at the Oscars for Best Motion Picture, "and I had moved to London during that period.

"So when we started to make the film I was very much in the midst of homesickness. There was that heaviness you feel, not quite knowing where you belong.

"To go through that at the same time as playing a character that is going through the same emotional journey was very gratifying. But it was overwhelming as well."

The experience was overwhelming because she worried about being too close to the character.

"I was worried that I wasn't acting enough because it felt so real," she explains. "Homesickness is like an illness. That's the hardest thing about it. While making Brooklyn, it was a new sensation for me to be playing a character that was going through a similar emotional journey as me at the same time," she says of the movie adapted from the Colm Toibin novel by acclaimed author and screenwriter Nick Hornby.

Even the nature of her own homesickness matched her character's.

"I miss my mum, more than anything," she says. "In the film, the scene where Eilis is saying goodbye to her mother for the second time, and probably the final time, was devastating for me.

"My mum's maiden name is Brennan and Jane Brennan is the actress who plays my mother in the film. Jane looks a little bit like her. So that was strange. I always miss my mum when we're apart. I also miss home-cooked food and proper tea."

As if the connections could not get any closer between actress and character, Ronan, who rose to prominence with her pivotal role in director Joe Wright's 2007 hit Atonement, also has a strong connection to New York. She was born in the Bronx before her parents moved back to Ireland when she was three years old.

"My mum and dad moved to America in the early 1980s for the same reason as my character in the film - for work. There were no prospects for anyone young back home at that time.

"That is kind of what the Irish do. We leave and then we come back. We are a nation of leavers. My parents went over there, had me and then we moved back to Ireland. So New York and Ireland are two, huge defining things for me."

Ronan has made a number of high-profile movies, including The Lovely Bones (2009), Hanna (2011) and Byzantium (2012), but Brooklyn is her first film about Ireland. It scooped the Best British Film award at the Baftas in London last week.

"It was the perfect first Irish project to do because it has that relationship with America that I was so familiar with," she says. "But it became so much more than that when we started filming."

Irish director John Crowley, a celebrated theatre director who made his feature film debut with 2003's Intermission, believes Ronan is the jewel in an impressive cast comprising Domhnall Gleeson, Emory Cohen, Jim Broadbent and Julie Walters, among others.

"There is not a version of Eilis I could picture outside of Saoirse," he says. "She has made it her own. Saoirse is an incredibly centred and powerful young woman. That's why she was deeply confused when she left home and felt the same things that Eilis felt; she was discombobulated.

"She was like, 'I shouldn't feel this; I have been coming to London since I was 10. I can go back to Ireland at any time. It is an hour's flight away, not a week on a boat.' The huge gap between who she is and who Eilis is collapses at that point because of the emotional trace of what she's going through."

Given her brilliance in the role, one wonders why Ronan had not until Brooklyn played an Irish character before?

"The roles just didn't feel right," she says. "I desperately wanted to make an Irish film because I am very proud of where I come from and I love what I do, so to combine the two things is perfect. But I didn't want to get involved in something just for the sake of it. But Brooklyn was a very personal story for me."

Brooklyn as a place will soon become as personal as the film; Ronan can explore the fashionable New York City suburb while performing in the production of the Arthur Miller play The Crucible, which is currently on Broadway.

"I won't be able to move to Brooklyn while I am doing the play," she says with a smile. "I have to stay in Manhattan because it will be easier to get to the theatre every day. But I think I will probably move to Brooklyn after the play is over.

"I love Brooklyn; it has a village feel. Ireland and New York complement each other so well."

At 21 years of age, Ronan's adult life is only just beginning, but she knows that whatever happens, she will eventually move back to Ireland, especially when she tries to start her own family.

"I love Ireland so much and I can't imagine raising my kids anywhere else."

• Brooklyn is showing in Singapore cinemas.