Toxic sister in law

So my sister in law came from Mexico maybe about 14 years ago. She has brought so many negativity to our lives. She’s very money hungry and very selfish. So unfortunately my brother cheated on her. Which was completely wrong of him. I don’t defend him on his actions. He only did it because she would leave to Mexico for years and he heard rumors about her that she did stuff with other guys from the guys she did stuff with btw. He never told us that but he came up front with my sister in law. Told her he fell in love with someone else without trying. However obviously that didn’t workout for him on both ends. So he decided to focus on his son and work. Anyways she’s very money hungry. She still stays in the guest house. It’s been 5 years that they have been separated. She only pays 300$ of rent here in California. She’s always downgrading my brother and she thinks very highly of herself. My brother hasn’t kicked her out because he feels guilty what he did so she still lives at the guest house with him. He sleeps in the sofa. They have a 14 year old son so he’s been through a lot. She doesn’t care for him. All she does is goes out and drinks with her friends ever since my nephew was a baby. We have raised him since than. She has tried to kick out my brother many times of our guest house. She has fucked him over with debt and she has done so many things I can’t say but can get her in huge trouble but we have no proof. My brother suffer the consequences and pays for them. Also yesterday she came up to me and told me I’ve done nothing with my life and she has achieved more things than me. She’s only been here for 14 years I’m nothing in life. I’m only 24 years I’m barely starting my life. I have graduated high school with high gpa. I’m working and paying for rent as well the same amount as her I only have one room lol 😂 not a whole house to myself. I only do it to help out my parents because they don’t ask for it. I also help them with groceries some bills. On top of me paying my own bills. Im going to school majoring in nursing going for my master is my goal. I’ve decided to start save up for apartment to see if I actually do it. Maybe save up for a down payment for a home. I don’t think highly of myself but I feel like I have achieved somethings. I don’t have my license because I can’t pass the test. I admit I’m not a good driver but I’m practicing. She puts my family down a lot when all we are doing is helping her out. She doesn’t even plan to move out or even get a house. She told me she’s not going to put herself in debt for a house here. The plan was she would only stay for so little because that’s the guest house. I just need to rant. I’m just frustrated with how she’s treating us when all we are doing is helping her out. I

Just don’t know what to do anymore. I’m tired of her stepping on my parents and taking advantage of them. They are so sweet and nice to her. When all she does is mistreat my brother and her son. Put us down talk bad about us. Idk what to do anymore. I’m tired of being nice.