Shefali was fighting to get Sana out of the house because of the physical violence she used.
Even though physical violence is against the rules, mental abuse is as big if not bigger. People might get over the slap they got but mental torture can leave an effect for a longer period of time.
So, as much as I like to see Shehnaaz getting kicked out on the bases of physical violence, I don't think the physical violence was any bigger than the mental torture Sana and everyone else went through.