It has been said before and will undoubtedly be said again: Rooney Mara is no fan of interviews. Those attempting to chip away at the chilly front she has presented in the past have described her, variously, as “glacier-eyed”, “aloof” and “impenetrable”.

Given I have limited time with her down a scratchy phone line, I am braced for the worst - yet pleasantly surprised by the buoyant mood the 30-year-old actress sounds to be in. To begin with.

Eddie Redmayne: 'Getting married was the most wonderful thing I've done'

Semi-fresh off a flight, Mara is sheltering indoors from a torrential New York snowstorm. A self-professed shy, guarded soul who steers well clear of social media, one gets the impression she might often prefer her own company to venturing onto crowded streets; snow or no snow. “I will have to take the dogs out, after this,” she laughs, ruefully.

The big, wide world is currently baying for many more glimpses of Mara, who has been weathering her own maelstrom of publicity, interviews and turns on the red carpet of late.

Though she was beaten by Kate Winslet to the best supporting actor gong at the BAFTAs, a fortnight ago, she may yet walk away this week’s greater prize: an Oscar for her role in Carol, the sumptuous tale of two women who fall in love in Fifties New York, when the American Psychiatric Association deemed homosexuality a “sociopathic personality disturbance”.

Mara plays Therese Belivet, a gamine, callow Audrey Hepburn-a-like who does a lot of staring and thinking. But still waters run deep and hers is an unsettlingly bewitching performance, beautifully offsetting Cate Blanchett’s firecracker of a role, for which she, too, was both BAFTA and Oscar-nominated.

Todd Haynes's Carol stars Rooney Mara and Cate Blanchett Credit: Festival de Cannes

Though Mara cut a striking figure in her Givenchy gown at the BAFTAs, the obvious question is: will she even attend the 69th Academy Awards on Sunday? The event has been engulfed in a ferocious diversity row since an all-white line up of nominees for best acting awards was announced in January, for the second year in a row.

So far, directors Spike Lee and Michael Moore, the actors Will Smith and his wife Jada Pinkett Smith have all publicly stated they will be boycotting the ceremony, #OscarsSoWhite has been trending (again) with viewers threatening to tune out altogether and British actor David Harewood, star of US hit Homeland, joining calls for those who attend to do so in “black face”.

Jake Lacy (Richard) and Rooney Mara (Therese) Credit: WILSON WEBB

“Yeah, yeah, I’ll be there,” says Mara, hesitantly, evidently unwilling to fully alight on such a hot topic.

In this, she seems wiser than Charlotte Rampling, who caused a fresh furore (and, some suggested, scotched her chances of winning Best Actress for her role in 45 Years) by declaring the deafening calls for diversity to be “racist to white people”.

But it would be unfair to imply Mara is maintaining a dignified silence in the hope it will prove as golden as an Oscar statuette.

“Here is the thing, I have a lot to say and I have very strong opinions about it, but it is such a sensitive issue I don’t want to reduce it to a sound bite,” she explains, clearly, of her refusal to be drawn further.

“I feel like that is what is happening. It is being turned into pull quotes and headlines, and that isn’t opening up a conversation so much as pointing fingers at people and taking their awards out of context. I don’t want to step into the conversation in that way.”

She has prior experience of such tricky conversations about Hollywood whitewashing. Last year, she was heavily criticised for taking the role of Tiger Lily in Joe Wright’s Pan - the character is Native American in both JM Barrie’s 1911 novel Peter and Wendy, and Walt Disney’s 1953 animated film Peter Pan. A petition to Warner Bros, objecting to her casting, garnered 96,000 signatures.

It was, she admits with understatement, a “tricky thing to deal with. There were two different periods; right after I was initially cast, and the reaction to that, and then the reaction again when the film came out.

“I really hate, hate, hate that I am on that side of the whitewashing conversation. I really do. I don’t ever want to be on that side of it again. I can understand why people were upset and frustrated.”

Rooney Mara as Tiger Lily in Pan Credit: Warner Bros.

Mara maintains that director Joe Wright’s intentions were “genuine” and insists she loved being part of the production.

Still, she says, “Do I think all of the four main people in the film should have been white with blonde hair and blue eyes? No. I think there should have been some diversity somewhere.”

Speaking candidly is not something that comes naturally to the emerald-eyed, chocolate-hued brunette, who you may (or may not) recognise as the fierce, pierced cyber hacker Lisbeth Salander in The Girl with the Dragon Tattoo (2011), which earned her her first Oscar nod, or the girlfriend who sassily dumped Mark Zuckerberg at the beginning of The Social Network (2010).

Nor do red carpets: “I don’t think it is ever something you look forward to. For me, it is an irritating part of the job. I try and make the most of it and have fun with it. But it is like this weird other thing. It has nothing to do with movies. It has become this thing unto itself.”

The relentless promotional tours, I suggest, must feel like a whole other job altogether. “Yes!” she enthuses. “When does that happen - that being an actor makes you a politician and sales person? I’m not good at either of those things. It’s not really what you sign up for. You have to learn how to, not be good at them, but get through them.”

Much like interviews it seems - as we swing to more personal matters, the shutters slowly but steadily close on her good mood.

The facts, at least, are these. Born and raised in New York, the third of four children, Mara (full name, Patricia Rooney) was inspired by the Broadway musicals and classic movies such as Gone with the Wind and Rebecca that her mother, Kathleen, took her to, from a young age.

Her older sister, Kate Mara is also an actress (House of Cards, The Martian and 127 Hours) whom she credits with encouraging her into the profession - although, no, they don’t practise lines together.

Keen to gain “life experience”, Mara went to George Washington University before transferring to New York University to study social policy and psychology. “I wanted to learn about other things that interested, because I wasn’t sure if acting would work out.”

She has a history of being both single-minded and level headed, and at university founded a charity now known as Uweza Foundation, which aims to lift street children out of poverty in Kibera, Kenya.

Her family tree can be traced back to County Down, Ireland, and bears genuine sporting giants: her father’s side co-founded the (American football team) New York Giants and her mother’s the Pittsburgh Steelers, although she does not relish being asked about it. And again, no, she never imagined going down a sporting route.

Enquiring about her love life is even less fruitful; I hear her audibly wince at questions about her boyfriend - director Charlie McDowell - or previous relationships that might have informed her portrayal of Therese in Carol. Her rebuttals are polite but firm - her voice gets quieter, her answers shorter.

Before the hatches can be completely battened, I chance my arm and bring up Aidan Turner: last year they filmed The Secret Scripture together in Ireland, the story of a woman who keeps a diary of her extended stay at a mental hospital. Surely she realises how pulse-racingly crazy we have gone for him, over here?

“Yes, I know all about it,” she says. “He is fantastic. When we shot the film it was right before this obsession grew out of control. We didn’t have that much to do together, but I really enjoyed working with him. You can see why all the ladies love him.”

Obviously, I explain it’s essential to know whether he took his top off during filming.

“No, he didn’t.”

Dramatic pause.

“He takes all his clothes off in this one.”

As she bursts into laughter, it seems - sadly - that she is finally joking.

Rooney Mara is nominated for an Oscar for her role as Therese Belivet in Carol