In Love and Other Drugs you play Maggie, a 26-year-old with early-onset Parkinson's disease who meets drug salesman Jamie (Jake Gyllenhaal).
It's unusual to find someone with a degenerative illness in a rom-com. How did you approach the role?
The most important thing was to make Maggie honest, and when I got the script she wasn't completely there yet but she had amazing potential to be angry, funny, smart and incredibly wounded. The thought of combining all of those aspects into a character was a challenge but very exciting.
You've said you always choose scripts with at least one element that "scares the bejesus out of you". What scared you about this one?
How eloquent of me! It was the sexuality of the character. I'm much happier talking with people than I am flirting with them. I'm pretty shy and not entirely comfortable with the kind of attention you get when you focus on your sexual side. I was afraid that I couldn't pull off playing Maggie.
The film also touches on the healthcare system in America and how a lot of people can't afford the drugs they need. Is this an issue you feel strongly about?
One of the things I like about the film is that it's not preachy. Without beating people over the head we show that a group of senior citizens and one sick young woman need to go to Canada in order to get their prescription meds. These people are sick and shouldn't have to go to such great lengths to attempt to be healthy. It's fair to say that we can do better.
So do you think President Obama was right to prioritise healthcare reform?
It needed to be done. From a social standpoint it was absolutely important. But whether it needed to be a priority? I'm not qualified to say, I don't know enough about the economics of running the country.
You were nominated for an Oscar for your performance as Kym, a recovering drug addict in Rachel Getting Married. Do you find that troubled characters such as Maggie and Kym stay with you?
I didn't shake Kym for a really long time. It sounds odd, but she was a good friend to me. Although in many ways she was trapped by her illness, she was also incredibly free and playing her allowed me to get in touch with that aspect of myself.
You made your name in The Princess Diaries. Is it a conscious move to take on grittier characters, ?
No, it's just what's available. But I like complex characters, so I seek them out.
Because of those films you've been frequently compared to a princess by the press. Is that annoying?
The question that I dreaded answering in interviews was "Did you always dream of being a princess?" I felt like saying "No, I dreamt of being an actress! That was a role I played!" It was frustrating because, like constantly being asked about the nudity in Love and Other Drugs, it kept the conversation at the surface. It was like talking to my grandparents – you know, "I'm really not as young as you think but I'm going to be polite".
So royal wouldn't be your fancy dress costume of choice?
No way! I go for things that are more sinister. Two years ago for Halloween I was a rebel angel who had been beaten up in a car accident.
Your mother is an actor and you were named after Shakespeare's wife. Did you grow up in an arty household?
Well, my dad's a lawyer with artistic sensibilities, so we were always encouraged to be creative but my dad kept us grounded in logic. We had to be able to make arguments and support them around the dinner table. "Arty household" suggests bohemia, kids running around naked, draped scarves everywhere – we weren't that.
Is there a Shakespearean role that most appeals to you?
I want to play the Shrew so badly. How do you make it so that it's an expression of love and not the subjugation of women? That's the challenge.
Have you ever been to Stratford-upon-Avon?
No, I've spent so many years working in England and I've never seen Anne Hathaway's cottage, can you believe it? I need to come on holiday.
Given that you're presenting the Oscars next year and you've just been nominated for a Golden Globe, it would probably have to be incognito. Absolutely. But you guys have such great style I could just dress all funky and try to get photographed by the Sartorialist.
Have you developed a bit of a thing for Britain then?
I suppose I have. My little brother spent a year at Oxford University and I went to visit him. He had to push me back into the car to leave, I was saying "I can stay. Really! I'll just shadow you in all of your classes, it'll be lovely. I'll cook!" It's a delightful country. People here are very good at finding a balance between doing their jobs well and enjoying their lives. I really felt that working on One Day.
Yes, there was surprise in some quarters when you landed the role of Yorkshire lass Emma Morley in the film adaptation of One Day. How did that come about?
I read the script before I read the book. It was one of those magical experiences where I sat at my kitchen table, looked up hours later and dinner had been eaten around me. I was so engrossed. It was absurd to think that this beloved British character would be played by an American but I told my agent I have to play Emma Morley. In terms of huge fish to tackle, Jane Austen in Becoming Jane was pretty big, so if they forgave me that maybe they'll forgive me this.
I've heard you're an avid reader. Aside from One Day, what are your books of the year?
Just Kids by Patti Smith is one of my favourites, and I turned vegetarian after reading Eating Animals by Jonathan Safran Foer. I'd been a shoddy vegetarian for years – I understand meat is delicious, I'm not insane! I just feel like less of a hypocrite now.
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