Nimboli feels attached to Mangala/Kamli since she perceives them to be equally victimised as she is. And being victims of the atrocities of Akheraj and Harki, they are sailing in the same boat. Therefore they become natural allies. Does not mean they think alike. Just means that presently survival in this house takes precedence over their inner abilities.
Their real colours will emerge when they are left to grow in freedom.
Kamli has shown she is still helpless and needs guidance from Pushkar's mom to take any step. But she is well-intentioned towards Nimboli.
Mangala, even if she leaves Akhi's house, she will still not do anything for herself. If she could, she would have already done it.
Nandini/Nimboli, who is presently just 11 years old, tries to find a way out when put in a difficult situation. She will soar when put in a conducive environment. What has been happening to her until now is just a way of life for her. She has not known any other. According to her all beendnies get beaten up and work the whole day long. Some more than others. Nothing to fret about.
The day she realises that Akhi's house is nothing but a cage, she will endeavour to escape, not wait for Akhiraj's "paap ka ghada" to fill to the brim as Mangala is doing. She may take Mangala too along with her or Mangala may give up her life in order to give Nimboli a head-start. That Mangala can do.