Well I think the issue is not about sonakshi knowing anything about it or not , the thing is , before marriage, it's a good thing that a mother opened up about this thing to her daughter...that was a good message sent..that parents discuss these things ..they must.. at the right age and the right time..
Well the whole point is why does the mother think that 28/29 is the right age for her daughter to get the talk (that too after the maid of all people reminds her) about 'what comes after marriage?'
I mean does she really think her daughter has reached almost 30 years of age without knowing about the birds and the bees? If she does think so, then that only reinforces the predominant thinking in our society that girls need to not only stay virgins till they get married, they also need to remain unaware about what happens in the act of sex. Above all girls must never have any sexual desires of their own because that makes them 'bad'. They just need to follow where the man leads.
So, let's assume Sona didn't get married till 35. Even at 35 her mom would have thought it appropriate to give her this talk? Please, that is just stretching it a bit too far...
Another thing I hate in all our serials is the woman always pushing the man away when he comes near saying 'chhodo na'. She has to coyly refuse the man's advances because that's the 'proper' thing to do. She can never just give into her desires can she?