I think it was valid this time.. It was one time too many where komolika has directly tried to harm prerna's baby.. As long as this is a one time thing and prerna doesn't start sprouting mamta and tyaag ke dialogues at every turn, I'm OK. Physically slapping someone who is trying to deliberately kill your child is a very acceptable reaction, I feel DG.
I am not talking about the slapping part ...i felt the knife part was OTT😲