Brothers wife is mentally torturing me and my widowed mother

Hi My elder brother got married about 3-4 years ago. After 6 months of marriage the relationship between my mother and my brother's wife went sour. Out of frustration, my mom told both if them to leave the house (the house belongs to my mom). Till now they are staying alone on rent (whose amount my brother pays from a rent we get from a shop co owned by both of us). My brother's wife does not keep proper care of him, she goes to her maternal home every 15 days. My brother's salary is only 8000, she also complains about that. He is mentally abused almost daily by her. They also have a kid. She is also keeping her dead brother's kid with her and my brother. She is constantly bothering and harrassing my mom to build her a new house. My mom constantly asks her to stay with our family in the same house, but she does not agree as she wants to keep her brother's kid with her too Yesterday I went through my brother's phone. In one call recording she was abusing him for telling him lies, degrading him, saying he only wants to sleep with her. Because he did not have money for rent. He asked our mom for money, but she refused as we had already given him plenty of money till now. She told her ki apni maa k gand me bharo. Usko apne niche sulao. Mai to tumko tumhari maa aur bhai ko nikal k vaha rahungi aur tumhare saamne 10 logo k saath soungi. She also said that my brother has more than one dad. She says that she will divide the house using wooden planks and stay there anyway she likes. Day before Yesterday she and her brother came to our house and told us to make a seperate house for my brother and her. If not we will handle the issue their own way. MY mom has a metal wall in her heart and her physical condition is not that great. My brother also lies a lot to his wife because she leaves her every 10-15 days and goes to her mothers house. Any help will be great. Please