You mean BWA? Why is Amma in jail then? I think she plants drugs or stolen money/sarees etc from Pallu's shop in Amma's house.. gets them arrested for theft or drugs peddling. And has the FIR registered on Pallu's name.
If BWA really wants to get back at Pallavi, she can expose her shop accounts lies infront of the whole family... Yes that could be a reason for Rambo to kick her out.. but that doent explain why Amma Keerthi go in jail and Raghav doubts Pallavi to be behind it.