In the film, directed by Ashwini Iyer Tiwari, the 27-year-old actress is playing the mother of a 15-year-old girl.
"When the casting director Mukesh Chhabra came with this idea of a mother-daughter film, I thought I had to play the role of a daughter. I was shocked and told him that my career will go down as it's a mother's role," Swara told reporters here at the launch of the trailer of 'Nil Battey Sannata'.
The film, backed by filmmaker Aanand Rai, and also featuring Ratna Pathak, Pankaj Tripathi and Ria, will release in theatres on April 22.
"I had played Salman Khan's sister (in 'Prem Ratan Dhan Payo') and then I get to play a mother (in Nil...) soon I might even get offer for the role of a grandmother," she said in a lighter vein.
Swara said that actresses typically play roles suitable to their age or roles of younger people.
"There were people who told me it's not a good idea to do this role. I was scared about my image," the actress said, adding that when she read the story of the film she fell in love with the idea.
Swara said she had initially thought of refusing to play the role.
"I thought I will just read the script as the casting director is a friend and say that I did not like the story. But rather I loved it (story)," she said. Swara said she was told by the director to gain weight for the role.
"I was asked to gain 10 kg. So I kept eating and eating. But midway through the shoot, she (Ashwini Iyer Tiwari) told me to lose some weight as I was looking a bit too healthy. It is difficult to lose weight," she said.
Explaining the title of the film, Swara revealed that in real life she is "Nil Battey Sannata" ('being an absolute zero or incompetent') when it comes to glamour. Swara considers walking the red carpet is like appearing for examination.
"To be a heroine is an occupational hazard. Earlier, I used to not pay attention to it (glamour side). Now I do my homework as we have a team (stylist)," she said. Considering that she has worked with fashionista Sonam Kapoor in "Ranjhaana" and "Prem Ratan Dhan Payo", Swara said she talked girly stuff with her. Swara, however, said that actors are remembered for the work they do.
"It was great experience of working with her (Ratna Pathak Shah). She is brilliant and an outstanding actress," Swara said.