Gabby Sidibe shows her Precious mettle

It has almost become a default reaction when talking about Gabourey "Gabby" Sidibe to mention how pretty she is. It has reached the stage where one suspects that adults are now trying to make up for their childhood playground taunts at the fat kid in class and are trying to prove that now they've matured they can see that big can be beautiful.

Yet it's not the size or looks of the 27-year-old that are her most impressive claim to fame. Plucked from the streets of Harlem, this unknown actress came out of nowhere to be nominated for an Academy Award for her acting debut in Precious, and so became one of only eight African-American women to be nominated for the big prize at the Oscars.

In that film she played the title role in the adaptation of Sapphire's book about an illiterate, obese 16-year-old girl with two children fathered by her rapist father. It had everything to do with Sidibe's performance that the film became the sleeper hit of 2010.

The two big questions that arise whenever anyone comes in from the cold are whether they are going to be one-hit-wonders or a staple on our cinema screens over the next decade. The indications are that Sidibe is going to be a big star of our screens for a long time to come.

She is a star on the Showtime TV series The Big C, playing the mouthy, combative, student Andrea Jackson, and has also hosted Saturday Night Live. Now the cinema acting gigs are arriving fast. First up is Yelling to the Sky and then the Promised Land of Hollywood blockbusters is reached with a starring role in Brett Ratner's Tower Heist. It's easy to see why director Victoria Mahoney would want the Brooklyn-born star to appear in Yelling to the Sky. The film, like Precious, is about a young girl struggling to survive in New York City, although this time Sidibe is playing the bully and aggressor rather than the victim. In another connection with Precious, Yelling to the Sky stars Zoë Kravitz, daughter of Lenny Kravitz, the rocker who played Gabby's unlikely boyfriend in Precious.

Sidibe says that, having known Zoë Kravitz for some time, it was weird to play her enemy. "Being mean to each was definitely not a plus of this part. That's a strange aspect of being in this film together, because we play enemies and that can get really strange, and we are both sensitive people with plenty of emotion, and the emotion we have to get into in order to have to get into this and fight is very hard to do with someone that I love, and someone that I care about, and someone that doesn't bitch – and that is really strange, but it was really cool to hang out on set and be able to do girl talk: that was best part for me."

After she shot the scene in which they fight with each other, she admits that she and her co-star broke down, crying. It's another example of the amazing intensity that she brings to her role. The irony is that the vibes she gives out off screen could not be more different to those displayed by the characters on screen. She is always cracking jokes and seems incredibly smart.

She has made a seamless jump into stardom. The star says of her post-Oscar nomination life: "First of all I got this film, Yelling to the Sky, well before Precious came out and so I was already kind of in the midst of the beginning of my career. After the Oscars I started The Big C and now I'm doing Tower Heist, it's a lot like it was before the Oscars when I was just this working actress, and this wave that I seem to be on seems like such a grand thing for those on the outside, but because I'm on the wave, it doesn't feel like a wave but more like life."

She tries to downplay the life-changing aspect that has come about in the

past year: "My life is kind of normal as a working actress. It's not normal for a teacher or student, but it's kind of normal for a working actress."

It's only when pressed that she admits that it's a little out of the ordinary to be recognised everywhere she goes. "More people know me than I know them and that is not normal," she says. "It's certainly is strange and it's not without its scariness. It makes me feel strange to say that I have fans and it makes me feel strange to say that I'm a celebrity, because I don't believe that I am. I just think that I'm a girl with a job that everyone can see."

It's then she finally starts on the downside, and her fame in America becomes apparent.

"I walk around New York and I ride buses and stuff like that, but I do it at a much slower pace, because every fifth person I meet I have to hug, or sign autographs or take pictures and things like that. I wear a hat and sunglasses so I don't have to do it as much. But I still get recognised. I was in a store with my face completely hidden except for my chin and someone comes up to me and says "Are you Gabby?" and I was like, 'Really! How do you know who I am from this chin?" I guess what I'm trying to say is that I'm as normal as anyone can be for someone who was on every TV screen last year."

One suspects Sidibe's frame may have also helped the starry-eyed fan to spot the talent. But with fame also comes great interest. So much, in fact, that she says that she has to turn the TV off when she sees herself on screen. It's a big difference to the woman I met for the first time a year ago, just as Precious was premiering at Cannes, when she said: "I love it, especially the red carpet... I like doing it because every time I've got to go and do make-up"

Now the actress is asked to give a daily commentary on her life, from the lip-gloss she wears to speculation about her boyfriend. She has successfully kept him out of the media, stating that he's a normal guy, but the media in the US went crazy last month when she was spotted at a basketball game with her beau. He was not famous and fans and media became obsessed with trying to find out his name. So – who is her boyfriend? In a heartbeat Gabby gives a response that completely renders the line of questioning futile while also raising a laugh: "I'm dating Colin Firth," she jokes. "We were trying to keep it secret, he is going to be so mad at me. I need you to know that we are dating and it's all about the Oscars." Later on in the conversation her phone vibrates and when she looks at it, she quips, "Oh Colin's calling again, ah baby, he misses me."

It's a brilliant example of her sense of humour, which, she quips naturally, was "bought on eBay." It also helped her handle all those Oscar parties, "It was one long party, and I wasn't really concerned with winning and losing because there is no time machine that I could have jumped in to go back and make my performance any better. But at the same time, it was like if you have 10 office parties in a month, at some point you say 'Christ, another party'. It was so exhausting and I was so excited about the Oscars just because it meant the end of everything and I could finally switch off. I went home and slept for 30 hours straight as soon as the ceremony was over."

Her sense of comic timing has also been recognised by Hollywood, and she has just completed filming her first big Hollywood film, Tower Heist, in which she stars with Ben Stiller, Eddie Murphy, Matthew Broderick and Casey Affleck. All she says about the plot is that it's about workers in a building trying to steal from the "big cheese" and that she's in on the crime. It was, she says, a test of her self-confidence and, especially, her ability to be funny.

"I was really worried because a lot of my scenes are with Eddie Murphy, and all I could think about is Raw, and how genius he is in that with his red leather suit, and he's so funny, and I was so nervous about what it would be like to film with him. I'm toning it down today but I am actually quite a raunchy and crazy person, and on this film I was allowed to be a crazy person."

'Yelling to the Sky' is out later this year