"Every time I talk about it, I get teary-eyed. It becomes very difficult for me to talk about it. Doing something like this to any man, woman or animal is deplorable. To honour someone, who was courageous and fought a battle, is brilliant," Sonam told reporters here.
The 23-year-old, who was brutally gang-raped and tortured in the Indian capital, died in December last year.
Nirbhaya is among 10 extraordinary women who will be honoured on the occasion of the International Women's Day Friday with the Secretary of State's International Women of Courage Award by Michelle Obama in Washington, US.
Nirbhaya will be awarded posthumously and Sonam said it will give give "publicity" to her, which is needed "because people tend to forget it".
"When something like this (rape) happens, there is a lot of hue and cry, but later it is forgotten. This honour will make the incidence fresh in our memory," she added.
The 27-year-old was in the capital Thursday to announce the second edition of L'Oreal Paris Femina Women Awards 2013.
Honouring women with extraordinary accomplishment, outstanding leadership qualities and exceptional commitment to their careers, the awards will be held March 19 in Mumbai.
Sonam, L'Oreal Paris's brand ambassador, said: "The most powerful people in our country are women and we need to encourage them, who are doing so much for art, culture, and society."
She has been shooting in the capital for sometime now and believes education is important to change mindsets.
She says that as a woman she has the freedom to move around in Mumbai on her own, but her movement gets restricted in the capital.
"I am shooting in Delhi for the past six month. As someone from Mumbai, I go out whenever I want to. But when I am in Delhi, I know I can't go out after 7:30 p.m. on my own. We cannot blame a city. The basic thing required is education.
"It is about being open, aware and start respecting women. I think illiteracy is the biggest cause of this kind of mindset. I think once people get more educated, things will change," said Sonam.
She is currently shooting for Yash Raj Films' untitled project with actor Ayushmann Khurrana in the capital.