Blackmailing by my father's second wife

My father passed away 3 years back and mother 2 years back and are survived by 4 children. My father had a second wife - Mrs X (not sure if she has a proof of wedding) but she lived with my father for the last 30+ years and has 2 children.. While we are in possession of my father's ancestral property, my father left the following for Mrs X. 1. A house in which Mrs. X sold and purchased house in another city after my fathers death. 2. A plantation worth around 8 Lakhs, in our control at the moment. 3. A house in Noida worth 60 Lakhs which in currently in my name. Now Mrs. X has been demanding Rs 15 Lakhs for the plantation and the transfer of the house in Noida immediately else she is threatening with revealing personal details of my father, his affairs, scandals, etc. to our extended family and relatives and that she will come to our house and create a reckus. We dont have much problem giving her the house+Rs 8 Lak, what we are worried is that blackmailing may continue in future.