Copying her mother's behavior probably isn't the best way to help the child? Her new school would presumably need to know how she has been doing, as her mother will not be able to tell them.

Sure get angry with the mother, but why take it out on the child?

Maybe you could apply to be a registered foster carer, most foster children do actually return to their birth parent/s. But part of the procedure in registering you would entail 'seperation counselling', so you would know how to act in the best interest of the child when they leave?