So ignoring that part ... Sheetal telling Khushi not to tell Arnav ... did she really expect her not to? And just walk out quietly? Or did she fully expect Khushi to tell Arnav? Then, if Arnav has really not slept with Sheetal ever, her game is up ... he will know she's playing mind games with his wife. So to progress the track, Arnav has to have slept with Sheetal at least once, or at least Sheetal has to have some incident up her sleeve to convince him that he did ...
And so ... Sheetal will play Arnav to convince him that all this is in Khushi's mind ... he will be angry with Khushi that she hasn't trusted him and is still stuck on the "Arav is your son" mantra ... will he bond with Aarav out of anger with Khushi? And distances between Arnav and Khushi grow ... but slowly Arnav comes to realize that Sheetal has been playing both him and Khushi ... and he plays her game back with her ...
I would expect that Khushi goes all quiet, rather than harangue both Sheetal to tell the truth and Arnav to accept it ... thus widening the distances ...
That is, of course, if the story goes the way it should ... the rest depends on what happens offscreen ... wait and watch is the mantra, I guess! Again, no role for Nani, Mami, Anjali? No wonder they all want to leave!