This was part of uncensored videos as to why he did that.
That was because Mandana was abusing him and he gave up and started returning her the same favor.
It is not a proud moment that Rishab did those hand gestures. But at the same time, cannot criticize him for that because he was showing the same thing in actions as to what Mandana is doing with words.
Mandana could not say anything in reply because she knows she started this rubbish.