With her 18th Oscar nomination, Meryl Streep's hit the record books - but it hasn't come easy. The actress tells Shereen Low why playing a bitter cancer-stricken sufferer in August: Osage County was one of her most challenging roles to date.

"Women aren't sexy when they're old," declares Violet Weston during a vitriolic rant in August: Osage County.

But one look at Meryl Streep, the actress who portrays her, and you realise that she, at least, certainly defies that remark.

Oozing elegance in a black blouse and fitted trousers, her blonde hair tidied away from her face and barely any lines or wrinkles on her glowing skin, the Oscar-winning actress looks a decade younger than her 64 years.

Chuckling at the unexpected compliment, a bespectacled Streep says: "The world will tell you that is true, but individually, we can defy the world's wisdom."

The star of films like Julie & Julia, Mamma Mia! and The Hours has made history after receiving her 18th Oscar nomination for her performance in the big screen adaptation of Tracy Letts's Pulitzer Prize-winning play.

She already has three golden statuettes in her possession (Best Supporting Actress for Kramer Vs Kramer in 1979, and Best Actress for Sophie's Choice in 1983 and The Iron Lady in 2012).

Julia Roberts, who plays Streep's daughter Barbara in the movie, is also up for a Best Supporting Actress Oscar and Bafta.

"I'm so happy for our film, that Julia and I have been nominated. We're both so proud of August: Osage County," says Streep, adding that it's "thrilling" that the awards buzz will help attract more people to watch the film.

Things could have been very different, though - she turned the part down at first.

"I said no, I really did," the softly-spoken actress admits. "But they dragged me in, kicking and screaming," she adds, smiling.

Streep is no stranger to portraying 'hard' women - after all, this is the actress who took on the opinion-dividing former Prime Minister Margaret Thatcher (The Iron Lady), tyrannical magazine editor Miranda Priestly (The Devil Wears Prada) and an accusing nun (Doubt) - but she wasn't sure about sharp-tongued, pill-popping cancer-stricken matriarch Violet.

The story revolves around Violet's strained relationship with her family, as they reunite following a crisis. Tensions build as previous clashes are rekindled - one scene even sees Roberts strangle Streep as the two women come to blows.

"I said no, because who really wants to sign up to know what it feels like to have mouth cancer, children that hate you, a husband who'd rather kill himself than be in your presence, and chemotherapy, pills, misery and a horrible past?" Streep continues.

"To crawl into that head and that heart, argh! Because part of that pain, you realise as you get older, is these things cost you more, in a weird way. You carry them home, you feel you bleed more easily with it."

Director John Wells understands why his leading lady had her "reasonable doubts".

"The role is, on a day-to-day basis, a difficult place to be," he notes. "Violet's bitter and sarcastic, a holy terror to everyone who comes into her path. Meryl is actually a personable, kind, gentle person, so day after day, she was attacking all these people that she likes."

Streep was eventually persuaded to sign on though, when she heard who her co-stars would be. The film also features Juliette Lewis (as youngest daughter Karen) and Sam Shepard (husband Beverly) as well as Ewan McGregor, Chris Cooper and Benedict Cumberbatch.

"It's a great part and I thought, 'Hell, such a cast'. How could I not?" Streep says, adding: "I fell in love when I met Benedict. Everybody does! He's so dear."

Many of the cast, including Cumberbatch and Lewis, admit to feeling star-struck at the table reading, where they were joined by playwright Letts and producer George Clooney.

With over 30 years' experience on the big and small screens, as well as on stage, Streep didn't get the jitters, surely?

"The table reading was, yeah, a kick," admits the New Jersey-born mother-of-four, who is married to sculptor Don Gummer. "I had never met Tracy Letts. I adore actors but I am always in awe of writers and most scared of them, and disappointing them, certainly in the first read.

"Here was a Pulitzer Prize-winning playwright and I was about to mangle his creation. We all felt that. Plus the first table read was with Sam Shepard, who's playing my husband, and it was another writer that I admire. So there was a lot to be nervous about."

If initial reactions are anything to go by, Streep has nothing to be nervous about. As well as the record-breaking Oscar nomination, her performance has met with rave reviews, and once again, she pulls off a remarkable visual transformation as Violet. The non-smoking actress also had to light up for the part - Violet's a chain-smoker, and Wells recognises that it was a physically demanding job.

"A lot of days, we'd finish and she [Streep] would look at me and say, 'This is really hard'. But the commitment to that performance is part of what makes it a truly memorable and classic performance of hers," the director notes.

During filming, it was Streep who brought the cast together, and became the unofficial 'matriarch' of the group.

Co-star Lewis reveals: "Meryl wanted us all to live in a house together, but they couldn't find a house big enough, so we lived in these identical little condos next to each other.

"We'd go to Meryl's at night and have potluck dinners... We'd just hang out and share stories. It was pretty great."

Streep didn't have to look too far for her research and preparation for the role.

"Sadly, I have friends who've had cancer and I have friends who were having chemo, and I checked in with them about what that felt like," she says.

"I have friends who are drug addicts and I witnessed people trying not to do drugs and not being able to, and people being their worst selves because of drugs. I just checked in with my wide circle of acquaintances and everything I know about myself that I would be ashamed to have walk in front of me, just to let that out.

"So it was a horrible little hot-ball of burning lead that I carried around in my stomach for a while, but there is also great pleasure in knowing it's fiction," she adds.

"You can close the door on it at the end of the day. You can ride home for an hour in the beautiful Oklahoma landscape, listen to music and try to wash it away until first thing tomorrow."

Extra time - Not-so-happy families on film

:: Meet The Parents (2000) - Robert De Niro delights in making his future son-in-law Gaylord Focker (Ben Stiller) squirm in this entertaining comedy.

:: Little Miss Sunshine (2006) - Steve Carell, Abigail Breslin and Toni Collette star in this Oscar-winning comedy about a dysfunctional family heading to California on a road trip.

:: Running With Scissors (2006) - Starring Annette Bening, Joseph Fiennes and Evan Rachel Wood, this film's a semi-autobiographical account of Augusten Burroughs' unconventional childhood.

:: We Need To Talk About Kevin (2011) - Lynne Ramsay's silver screen adaptation of Lionel Shriver's dark novel, starring Ezra Miller as a teenage mass murderer and Tilda Swinton as his mother, was critically acclaimed.

:: Stoker (2013) - Matthew Goode plays a murderous uncle alongside Nicole Kidman and Mia Wasikowska in this chilling thriller.

:: August: Osage County opens in cinemas on Friday, January 24