Yesterday's episode showed that Mangala holds the upper hand in the form of the trump card --She enjoys Nandini's full trust, and enjoying everyone's discomfiture each time the child calls her "Ma." She can dictate the terms of her stay at BH, and monitor Nandini's interactions with other members. In other words, members of BH are in for an unpleasant treat with Mangala's strangulating love for Nandini.
Furthermore, with the use of a single weapon, namely Nandini's hatred for her mother, which Mangala herself fueled, Mangala has cleverly avoided punishment and being prosecuted/imprisoned for abduction, distanced Nandini from Anandi, and made herself indispensable in Nandini's life.
I am concerned that if Mangala starts to feel uneasy in terms of Nandini getting too comfortable or forging new bonds of love at BH or SN, she might kidnap her and run away again. This is something that Jagya and Anandi, and the whole family has to be on the alert for.