Baby Misthi's entry was shown saving her fellow children. That's enough to say how good she is.
Misthi from her childhood sticks to her priorities. She always wanted Ishan and she got him till the end.
Misthi is a little flawed, particularly when she is angry. She was rude to Pari and Kunal when she knew kunal left her for Pari and her mom.
As Misthi grew up, she lost her mom and popsie And was loaded with responsibility.
And now, she is so scared about her life being like Kunal-Mouli. She hates to be Nandini / Kunal.
We all may think she had popsie so she shouldn't worry about Dr. Kunal.
That's not so easy.
She is not feeling bad that she dint get Father's love. She never ever said she missed the "father in her life. She is scared / upset about things happening to her like her mom.
We all know and even Misthi knows her mom got second chance through her popsie but she is still scared not because she is not happy with Ishan-Mouli but because she isn't sure she will also get a Ishan if she is left like Mouli.
Her mom was lucky enough to have Ishan. How can she be sure she will be that lucky? So she is taking precautions, not because there is no cure but because prevention is better than cure.