What do I do about my brother's girlfriend?

This is going to be a little long because I am also venting. My brother has been with this woman for 8 years. She moved into the house that has been owned by my family for over 45 years, right after I moved out. This woman gives *itch a whole new meaning. She has driven a wedge inbetween my older brother and other members of my family. I recently had to move back in with my 11 year old son because I lost my job and am having to fight for unemployment. We live in a room that was built onto the patio years ago. I understand that she is the only one working and paying bills and I am grateful. But that doesn't give her the right to act the way she does. She locks the door at night a lot, I've had to pee in the yard and so has my son. I have to do laundry when she forgets to leave stuff in the machines. She hides my mail sometimes. She says horrid things to me, which I put up with to keep the peace. Recently she decoded it was ok to talk to my son like that. Last night she started in on him for taking a shower when they were all having dinner. He came to our room crying. I wanted to rip her head off. I've said something to my brother. He's said something to her and she will stop for a few days but then starts again. I'm going to have to say something but I have a feeling she will do something nefarious. But I will NOT put up with her doing this to my baby. I do help out around the house and when I do have money I hand it over to my brother. Any advice?