Nandini is the only daughter of Madan's sister Sangita's brother. How is Nandini related to Madan?

Madan's sister is Sangita. Sangita's brother is Madan himself. So Nandini is the only daughter of Madan, which means she is Madan's daughter. On final checking, the matching option is $\text{Daughter}$, which is option $A$.