It's reported that Kareena opted out of the film because she was not comfortable

"It is strange Kareena was not happy with her role. She also told Ekta and Karan that her wedding would be around the same time they wanted to start shooting for the film. It's a heroine-oriented film and Emraan is not the mainstay of the project. Deepika was so excited about her role that she agreed to it a couple of days before boarding the flight to Turkey, where she is currently shooting for Race 2," a source close to the Balaji-Dharma project told Mumbai Mirror.
Interestingly, the Heroine star later changed her mind and was prepared to do the role, though by then Deepika had already been finalised as the film's lead star.

According to the source, the filmmakers were convinced that Deepika will do as much justice to the role as Kareena would have. Deepika will next be seen opposite Kareena's beau Saif Ali Khan in their upcoming film Cocktail.
The film apparently has a women-centric theme and is an urban take on love - it is quirky, edgy and dramatic. It is directed by debutant director Akshay Roy, who is already working on the film.
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