Doughter in law (Bhabhi) mentally harassing whole family.

Doughter in law (Bhabhi) mentally harassing whole family specially harassing my mother mentally who is very old in her 60's.She fights with her husband (my elder brother) every night in a closed room. My doughter in law's (Bhabhi) family is denying and not taking any responsibity and cut the connection with us. She everyday fights with whole family and threats and warns us of taking unappropriate steps like suecide and she also pushed my mother once when she went to calm her down. We are not feeling safe in our own house and her husband is monitoring her closely leavu'g everything to prevent/stop her taking any unappropriate steps like suicide. Whole family is tensed and are not sleeping well from last 1 and half year. We have given her many chances that she will adjust and live happily with the family but no, she is still fighting for silly and small things and warns us of taking unappropriate steps like suecide. Please guide me how to approach the legal to get free her.