i think the lady defiantely is nikila!!!!
but gauri wont have the chance 2 find shashank, bcoz if its nikila shes gna stop gauri from going in there, obviously by being nice to her and diverting her attention, but judging by looking at the end of the epi, i dnt think she will get to find shanks in the basement. nikila will stop that if she is the culprit