let me add my two cents worth too...
Pia gave the man three chances already... First when she came to know about it, when Anand despite assuring her he will not, continued his relationship with Ratna
Second was when she gave him an ultimatum of one month, and Anand rejected it when he confessed to him Mom that he cannot live with Ratna and their relationship had progressed far beyond that stage..
third was when Piya left home and rejected Anand, Anand immediately went to seek solace in Ratnas arms.
Anand has repeatedly proved that he does not respect Piya.. why should Piya go to some man who has no respect for her wishes or feelings. Ultimately, she is a financially independent woman, an independant thinker and there is no reason for her to accept Anand at this juncture of her life today.
Would it be fair to Ratna if Anand left her in favour of Piya or any other woman.
Well, the saying "What you sow, so shall you reap" is true after all. RAtna was always aware that Anand was Piya's husband, yet that did not deter her from entering into a relationship with him. If she does not respect fidelity, there is no reason why she should be given that. "An act is a sin the first time, second time onwards, its a way of life". The first time Anand cheated on his wife for another woman, he has probably sinned and broken his marriage vows.. vows which are sacred. Having been broken once, whats the sactity in them.. nothing. So why worry if you break it repeatedly... none. In fact, it may quite be likely that Anand would tire of Ratna sooner than they would like to believe and may end up looking for greener pastures all his life.... a kind of vagabond existence, with ties to none.