There is a dialogue in Doctor Who where Amy talks about Rory and she says, "You know when sometimes you meet someone so beautiful, and then you actually talk to them, and five minutes later they're dull as a brick. But then there's other people, and you meet them and you think 'not bad, they're okay', and then you get to know them, and their face sort of becomes them, like their personality's written all over it, and they just they turn into something so beautiful... Rory is the most beautiful man I've ever seen."
And if any of you have seen Dr Who you'll know that Rory is not the type of guy you would call beautiful. But to Amy he is.
Just like that in the beginning Nandini looked so beautiful to me which she also is, but as the story progressed Mauli's personality cuteness and charisma
became her and all of a sudden Nandini even with her beauty started fading in the background and Mauli turned more beautiful than Nandini.
PS - No offense to the actors. Both Drashti and Aditi looks gorgeous.