Saoirse Ronan: Interview with the vampire

Saoirse Ronan is stifling a giggle. The recording device has broken mid-interview, and Ronan, the Irish teen star of Atonement and The Lovely Bones, is merrily finding an alternative on my iPad, as she tries to suppress the smile of a teenager faced with the technological ineptitude of an older generation. “There you go,” she announces triumphantly in the Dublin drawl she has rarely used on screen. “That's grand.”

It's rather a relief to see that Ronan is still a teenager at heart, albeit an extremely polite one. Having worked since the age of nine, she is possessed of an extraordinary maturity and polish, both on screen and in person, a quality that has led to her being cast repeatedly as precociously talented youngsters: budding writer, child assassin, benevolent teenage vampire. Byzantium, her latest film, will be her 12th feature. She's aged just 19, and every film-maker she has worked with sings her praises. Joe Wright, who directed Atonement, calls her “the most dedicated and focused actor I have ever met”. It's impressive – but a little intimidating, too, in someone so young.

And yet, there is something endearingly girlish about her. When I meet her, ahead of the UK premiere of Byzantium at the Glasgow Film Festival, she is curled-up, cat-like, on the sofa, dressed in thick black tights and a floral skirt – a youthful contrast to the glamorous woman who emerges later on the red carpet in stilettos. But Ronan is in need of adolescent downtime. On her 18th birthday, she did not, like other girls, go out for celebratory drinks. In fact, she did not do any partying at all, because she was on set in New Mexico.

“Actually, I've spent three of the last four birthdays working,” she says brightly. “I'm pretty used to it. And it was fun. The hair and make-up people decorated the trailer for me and they had a cake… I did have a pint of Guinness with my friends when I got back to Dublin, though.”

Ronan (her first name is pronounced Sirsha) works a lot. Born in the Bronx, New York, she moved back to County Carlow, Ireland, aged three, with her mother and father, Paul Ronan, also an actor. She already had a couple of low-key films under her belt, as well as the Irish TV series The Clinic (starring with her dad), when she got her break-out role, aged 12, as Briony Tallis in Atonement.

Based on the best-selling novel by Ian McEwan, the film earned her Oscar, Golden Globe and Bafta nominations as Best Supporting Actress, as well as the chance to work with Hollywood royalty: Peter Jackson in The Lovely Bones, Peter Weir on The Way Back, and Wright again, for child-assassin thriller Hanna. She had lost out on the role of Luna Lovegood in the Harry Potter films, but that hardly seems to matter now.

Doesn't she ever want to take a break? “Before I did Byzantium I had about six months off. But not working just makes me feel anxious. For me, having that daily routine, going on set, having the calendar tell me what time my pick-up is every morning... that's as normal as getting the bus to school would be to other people.”

She has six more films in post and pre-production, including Wes Anderson's The Grand Budapest Hotel, with a Who's Who of Hollywood A-listers: Bill Murray, Tilda Swinton, Harvey Keitel, Jude Law, Ralph Fiennes, Ed Norton. Earlier this year she played the lead in The Host, an adaptation of the book by the Twilight author Stephenie Meyer. Her co-stars said they would love to be appear in any sequels, but Ronan is typically cautious of committing to a franchise. “Um, yeah, I'd like to in theory but it would depend on the script. It always depends on whether the script is good.”

Ever the professional, little seems to intimidate her. “I am very focused. But I do also try not take it all too seriously. Gemma and I had a lot of laughs on set.”

By Gemma, she means Arterton, her co-star in Byzantium, a moody, modern vampire flick with the Interview with the Vampire director Neil Jordan at its helm and a strong feminist motif. Arterton and Ronan play a 200-year-old mother and daughter vampire duo, trying to settle down in a scruffy old English seaside town, while men, both human and vampire, get in their way.

Would she call herself a feminist? “Er, I don't know… There are a lot of people who say, yeah yeah, I'm a feminist and they're not actually. I wouldn't want to throw that word around because it's a very strong thing.”

What does feminism mean to her? She cocks her head to one side, characteristically thoughtful. It is important, she proffers, for younger people to see “strong, independent women” on screen, actresses such as Vanessa Redgrave and Cate Blanchett. “These are the people I look up to. Women who work hard and don't need to look perfect all the time. If that counts as feminism then grand.”

An only child, Ronan has been home-schooled since she was 14. Trouble at school, linked to her growing fame, prompted her to leave, although she says that reports of her being bullied have been exaggerated. She has great friends back home now, though – “who have always treated me normally” – as well as newer friends all over the world from places she has worked: London, New Zealand, New York. She likes to “just chill out”, sometimes play basketball or swim, but being on holiday makes her restless. “I can't sit on the beach for long. It's not a tanning thing, despite me being pale – I just get bored.”

In any case, she still gets on really well with her parents, and is in no rush to leave home. They recently stopped chaperoning her on set but still give their opinion on scripts: “I've never found them too intrusive, just helpful,” she says. A Lindsay Lohan-style post-teens breakdown seems distinctly unlikely. “My mam and dad trust me – and honestly, I'm just not that much of a party girl.”

So, what's next? She has yet to take her Leaving Certificate (the Irish equivalent of A-levels) but would love to go to university at some stage, probably NYU to study film or maybe History of Art. “New York feels like a second home to me, I think because I was born there. And I like the idea of not being on a campus, just integrating with the big city.

Work-wise she will soon step into Vanessa Redgrave's shoes as Mary, Queen of Scots in a new Working Title film (she hasn't yet seen the 1971 film starring Redgrave and Glenda Jackson but intends to) and work with Ryan Gosling for his directorial debut, How to Catch a Monster, due out in 2014.

Her porcelain skin turns a very slight crimson when I ask how she feels about working with Gosling: “My friend, she was like, 'Ooh, Ryan Gosling?!' when I told her!” There's a brief glimpse of the teenager again, before the composed professional takes back over. “It'll be a great experience,” she pronounces, sensibly. “And maybe after that I'll have a holiday.”

'Byzantium' will be released in the UK on 31 May