How do I get rid of my brothers crazy girlfriend?

I (23F) have a younger brother (22M) who has a beyond crazy (20F) girlfriend. This girl is genuinely a psychopath or has deep rooted issues. She’s extremely insecure which I do feel generally sorry about but her actions make me honestly hate her. There seems to be absolutely nothing she can do that will make my brother break up with her. A little backstory to my brother here but my brother is not really a good person. He is no innocent person in this story and I couldn’t imagine him being a good boyfriend at all. He was blessed with a mom that does everything for him and can see no wrong in him which you can imagine makes my life hell :) especially considering I’m the oldest and only daughter. That being said, I can’t do anything about having him in my life at the moment and i obviously can’t do anything about the fact he’s my brother. To add to that, we both still live at home because there’s currently a housing crisis where we live.

A little over a year ago my brother met his now girlfriend. I was delighted knowing my brother would be bringing over another girl to the house and I was excited to become friends with someone I could hang out with, drink with and have the odd gossip with butttt that was not the case at all. She is genuinely insane. Within the first month of them going out she stopped taking contraceptives without his knowledge and poked holes in his condoms without him knowing. Once he found out, which happened to be the day before his 21st birthday he broke up with her. The next morning, on his birthday she told him she was pregnant so they got back together. The following day she miraculously got her period and wasn’t pregnant anymore… and for some reason he still stayed.

Anytime we go on a holiday or outing with him she calls him non stop or texts him saying she’s been rushed to hospital. Anytime she comes to our house after a night of drinking she shouts at him at the top of her lungs and even goes as far as to open our windows and shout outside about how much she hates my brother (we live on a street with multiple houses). She has spread stories about other people in our village about how they’ve tried to rape her, about how they’ve hit her and would even spread gossip about others too. On one occasion she started a fight with this underage girl and the girls brother took my brother into the back of a van and repeatedly hit him with a hammer and left him on the side of a dirt road. Yet he still stays. She had multiple stds from previous people which she didn’t tell my brother about and he had contacted hiv from her. She has started telling my brother and my mom lies about me too and had claimed I said nasty things about them to her which wasn’t true. Any time he breaks up with her she threatens to take her own life or to tell the police that he hits her, rapes her or that he is a drug dealer. All of which I HOPE aren’t true. She’s done plenty of other things that would take too much time to say but I’m well and truly done with her and i genuinely don’t know what to do. My brother will not break up with her and my mom doesn’t want to enforce any boundaries or rules incase she “loses my brother” but I’m petrified if she gets herself pregnant and she is part of our lives forever. I’m not a prude or a snob but I don’t want someone like that apart of my family. I don’t want to think that she might some day take my dad’s last name. To explain that further, my dad sadly passed away suddenly 4 years ago and I was really close to him. I know my brother struggles with it and he had turned down a bad path when he died and I just feel like this girl makes it even worse. The best way to describe her is like a black cloud. She has so many insecurities and problems that she just sucks all the joy out of everything and she can be incredibly dangerous to someone’s mental health. She needs passwords for everything, he’s not allowed meet with his friends unless she’s there, he’s not allowed to go on trips without her, there’s been times where he would send me voice messages talking about every day life and you can hear her in the background like “who the f— are you speaking to?”

I don’t necessarily want her out of my life for my brothers sake because he has dug this hole for himself so many times but I need it for my own sake. I cannot deal with hearing shouting in my house at 3am every Saturday night. Or hear them arguing from his bedroom at all hours of the day. I know my brother isn’t a good person and he has probably done things that don’t help the situation like cheat on her or I don’t know, lie etc and in some ways maybe her actions are warranted or that she has these problems from real life experiences but it doesn’t justify why I have to hear about it every single day. What I’m trying to say is that I know my brother isn’t innocent and I’m not taking his side at all. It’s not like I want my brother rid of this toxic relationship because he doesn’t deserve it. But I cannot live with her constantly in my life and putting a dampener on it.

I really don’t know what to do. I don’t want to move out to escape it because this is MY HOME, not hers. I don’t understand why I should have to move out to escape my brother and his girlfriend. I’ve thought about calling the police on nights that she acts like this but I don’t want neighbors seeing the police pull up outside my home and come inside. I know it would embarrass my mom and I don’t want to do that to her.

Has anyone ever dealt with a situation like this and know what to do? I’ve texted his girlfriend on a few occasions to tell her to f— off when she was acting like this and she knows I don’t like her at all. I’ve even gone as far as to beg her to get out of our life but it was clearly no use. I’ve thought about getting a restraining order so it would mean she can’t enter our home but she hasn’t physically hurt me yet. My brother told me drunkenly before that she’s punched him on a few occasions but I know he would never openly admit it. I would take any advice please as I just have a feeling she will get herself pregnant and I will be DAMNED if she moves into our home to raise it.