I have noticed a trait in Nandini that she stays loyal with one person as long as she is getting something in return from them, when she sees a person who is better for her, she leaves the first one, this thing has been shown in two lights - Positive and Negative
Rajdeep was the parasite here but Nandini was stuck in a relationship and she couldn't let him go
When she was with Rajdeep, no matter what he did she never tried to go away from him, you can say he locked her or anything but someone in the forum mentioned how she paid his mistress then announced it in front of him thinking he'll be happy, you can say a victim or a loner was trying to cling to the one person she has in her life...
After Rajdeep, it was Mauli, Nandini took a decision to go against Rajdeep when she was certain that Mauli will be there for her no matter what so she went with Mauli, she made Mauli her world
Till yesterday, she was going over how she can not betray Mauli, but in last night's episode the moment kunal made her realize that he will be there with her and not Mauli, every concern she had for Mauli flew away because now she doesn't need Mauli, Kunal will be there for her so there's no need to worry about Mauli because she has taken all Mauli had to offer