My wife don't want my mother and niece to stay with us in house

We were nuclear family for more than 12 to 14 years, after my father past away, I have to shift my mother and dependent niece to my house. However, my wife don't want them in house, she always crib on small small matter and pushing me to ask them to go and stay in old house or with my sisters. Every day she find new trick to find fault in my niece work and blame her for whatever happen in house, in spite she help her in every aspect of house work that girl does in every house. If I tried to intervene ,she will be more aggressive and take out all anger on my mother , niece and son. I have one son age 10 year, she is not spearing him either, on small small issues she yell at him , she assault him while teaching lesson , he is getting scared and has to listen to her all the time. She once also tried to cut her hand but we could take medical help in time. We all are scared and unaware how to handle this situation , my sisters also kept my mother with them for more than 10 to 12 months but after her returning back , her motive is to throw them out at any cost. Unfortunately, my mother is 84 year old and her old hour is not in stage of staying because of heavy leakage and water seepage the condition of house is worst than godown and I cannot effort allowing them to stay alone in the area.