Sexual and emotional Harassment by family members what to do

I'm from Delhi , my gf was adopted by family. Actually , my gf's actual mother , was weak and suicided and father is weak too , and she got three sisters , one who is no more and the middle one is still there. But in childhood , her father , left her to his sister. That means she is adopted . Now everyone in this house hated her from past 19 years , she is bearing all these . His brother although is married , still harassed her on weekly bases. I'm with her from 1 year, and I'm aware about this thing , her smaller northern throws spit on her face and abuses about her dead mother on every fight. She is there because , her real father is weak both financially and emotionally . She is there only because she is helpless. No one , into even her big brother's wife , is aware about her harassment by brother. He touch her here and there and kiss too. But he is the only one who earn for the entire family and everyone is dependant on him for need. That's why no one would believe the he is guilty. What should she do?