As it is said that the two had a silent tiff between them so Divya was all set for revenge. Instead of acting, she slapped him for real and made sure there were as many retakes as possible.
According to the director of the film, it was actually a very funny incident and it was true that Divya and Randeep did have some differences between them and Divya left no stone unturned to get even with him.
He also added that he wasn't aware of the situation before the shot and only realized once they were done with it, but he agreed it was a very light hearted shot and not an intense one.
Divya would not normally taken so long for a shot, but as this was an exception, little to anyone's knowledge that she was actually enjoying herself. All through the while Randeep came out as a complete gentleman and was completely ok with what was happening. According to Divya, it seems she had already asked Randeep about it and he had agreed.