I do like how the story is about to unfold as it stands. Pari and Mauli are definitely going to get attached to each other. And I am okay with that because Mauli's struggle hasn't ended yet, she will still have to face some hard decisions before she can truly move forward with Ishaan. I am hoping at the end of the day, Mauli and Ishaan will prevail.
But, comparing Mishti and Pari's situations isn't fair to either of them. Mishti doesn't know her father. She is in blissfully ignorant about what happened with her parents and rightly so because she shouldn't have to concern herself with such adult problems at such a young age. And she is receiving fatherly love from Ishaan. Which a lot of children without fathers do no receive and I am so so happy that she has Ishaan. She shouldn't have to miss out on father's love just because her own decided he didn't want her. (In Kunal's defense, he doesn't know he has a child but that's another argument). In a way, Mishti does have love from her mother, a father figure, a grandmother and great grandmother. That is a lot of love. And coming to your point, Mishti doesn't know what she is unwanted and unloved. Maybe once she knows the truth then we can gauge the situation fairly.
With Pari, I truly feel for her. She lost her mother at such a young age. She obviously has a father but as someone mentioned above, a mother's love is deeper in a sense. And especially if Pari and Nandani had a great relationship, which seems that they did from all the food making lol. Of course it's kheer and pasta. Anyways, all Pari has in the world is Kunal. That is it. And she may also have to face the consequences and the repercussions of being Nandani's daughter given the circumstances with no fault of her own.