How can I keep my brother's girlfriend from coming to visit and staying with me & Mom, who I take care of, but refuses to get involved?

I live with my mom due to being on disability for the last 8 years. I don’t look or act disabled but I can’t keep a job because I miss a lot of days due to illness. My mom is 97 and has always been healthy until 5 years ago, my brother who has mistreated me my whole life, comes to visit about 3 times a year( and at Christmas for 2 was) and his girlfriend has been extremely condescending, rude and just awful to me and does it when no one is looking. It has been going on for 10 years. My mom and sister have always known but have never helped me because they tell me if I say anything to her that would upset my brother, my mom and sister would be furious with me and Mom would kick me out. It’s ridiculous. So last Christmas I finally told my brother, who did not fully believe me. But recently he talked with her and she admitted to having no respect for me, and that she is not going to treat me any different. So I told my mom and sister and my sister just rented a hotel room for the girlfriend to stay at instead of here at the house thinking it would help me so the girlfriend is not around. $1500 for the hotel room. They don’t understand that they are rewarding her for terrible behavior. And I am not allowed to talk about it or the way the girlfriend treats me. I told my mom that SHE is the one that needs to tell the girlfriend that she can’t stay at the house because of her behavior towards me. I have never done anything towards this girlfriend. I have always been extremely polite and kind. I have done so much for my mother. My whole life. I know she doesn’t want to say anything to the girlfriend for fear my brother will get mad and never come again. It’s humiliating that this girl gets to stay here at our modest but pretty house and continue to harass me. When the girlfriend first visited, my mom told her to make herself at home, and that she could eat our food and use our stuff. She doesn’t like me because she thinks I am lying about my health problems because I look like the most healthy person. She doesn’t understand my situation. I was never allowed to stand up to her because of the situation I described above. She apparently gets off treating me bad. It’s not my house so o can’t tell her to stay out, but I must have some rights since I have lived here my whole life. I am a caretaker for my mom and do EVERYTHING to keep the house clean and running efficiently and driving my mom everywhere, etc. so please, is there anyone out there that can give me some informative advice? I’m desperate and on the verge of ending my life. I am a good girl, intelligent, funny, pretty, and never was in trouble with drinking. Drugs, or the law. I don’t deserve this but I don’t have enough money to live somewhere else. I just don’t know what do to. It has stressed me to the point that I’m ready to end it all or go to the psych ward.