Domestic violence with sister-in-law what can i do

Dear Sir, I m Staying with my family & brothers family in same building but I m staying on first floor and brother staying at ground floor, my brother is Alcoholic and fighting with his wife on daily basis , his wife always telling me she will suicide and includes your Name too , in that scenario what i do for my safety purpose, i always tell her go to police station and file fir against his husband but she never goes..pls guide