My sister in law, threatens my father and mother

Hi all, My elder brother(age 30) got married 10 months back and he and his wife is staying with my mother(age 60) and father(age 59) Since then my parents are been threatened by my sister in law if her demands are not fulfilled, My brother does not take any stand and let the issue escalate between by parents and sister in-law. Few months back my sister in-law parents moved in our society and since then these issues are becoming a weekly scenario. Also she threatens my parents that she will commit suicide and the blame will be on my parents, due to which they are forced to keep quite and listed to her demands. My mother has high BP and depression issues and i feel she may get seriously ill, my brother is also scared of his wife anger and he also don't want to apply for a divorce and above all he don,t want to leave the parent house as he cant live with her alone. My parents are helpless and seeking an immediate support. Me and my wife also lives in the same society with my grand parents and recently have faced my sister in-law anger issues. She goes completely mad over small issues and call her mother who eventually supports her and guide her through phone. At times she breaks house stuff and even try to call the police and threats to log a false complaint of DV against all of us. We require help as my brother dont want a divorce, nether he wants to leave the house as he cant live with her alone. and we have no other options to fulfill her demands.