Makers did show them as grey. The lack of guilt, the utter selfishness, the total uncare for Mauli was their greyness. They knew they were wrong but they did not want to correct themselves. The difference between Rajdeep and them was that this two knew that they are hurting their close ones but Rajdeep would not even acknowledge that fact. Also, leaving the EMA aside, in all other facets of life they have been good people.I think the reason Nandini decided to resist is Mauli. Previously she knew she was going to hurt Mauli, she knew Mauli would be angry, and would break all relationships with her but I think she also thought Mauli is strong and will survive. But seeing Mauli begging was something that Nandini could not handle. The strong Mauli who has always been a rock for her, on the floor asking for Kunal as a birthday gift is something that Nandini's Mauli would never do and that was the last straw. Also, may be promise must be a very important tradition but it was seeing Mauli all broken and begging is what is making Nandini resist. That was her mirror of the devastation her decision was causing her friend.
[/QUOTEMauli is strong and she will survive, seriously, so strong women can be cheated, they don't need a man in their life. If the makers wanted to show ema , fine, they wanted to show two utterly selfish people fine again. But nandhini uttering dialouges like ,I hope everything is fine between mauli and kunal, mauli ko bura laga hoga , or arranging birthday party for mauli are all unrealistic.from the moment of revealation she has been uttering only non sense and that is exactly why the serial looks very unrealistic.