Arjumand, the daughter of Jahanara and Isa, is a sweet girl. (Don't confuse her with Jahanara's mom, who she's named after.)
She has a lovely temperament that makes her an easy kid to take to work, and she doesn't seem to have a problem hanging out with various adults who are acting parental figures. She's incredibly resilient, having survived an assassination attempt at a young age (thanks Balkhi and Aurangzeb, ya jerks), not to mention incredible upheaval as she's forced to flee her home and loved ones several times throughout the course of her life.
Arjumand maintains her rosy outlook for most of her life, despite these setbacks, so that even as an adult her mother is awed by her self-possession and good nature:
After returning from the sea, we swam at dusk, for dusk was when the waters receded and lessened in ferocity. Arjumand and I shed our robes, and wearing shirts and breeches intended for boys, we frolicked like sisters. As we swam, she told me of her building, in which she found great joy, and I spoke of Agra and her grandfather. It amazed me to see what a convergence she was between Isa and me. Not only did her looks reflect our merging, but so did her temperament. She had a clever mind, which I believed she inherited from us both. Moreover, she was feisty like me, and she also possessed Isa's youthful enthusiasm. This relentless good nature bound them strongly, and I knew, without remorse, that they'd forever be closer than she and I. (21.138)
Eventually, Arjumand becomes a mother herself, and her two daughters are the young women to whom an older Jahanara is relating their family tale.