How do i deal with my toxic roommate

I literally hate this girl, she is like 3 or 4 years older than the rest of us (we are 21-22) in a college apartment. She is not in school and just works. Not only did she allow a random girl to live in her room with her without informing us but she literally waits for me to say something off or do something off so that she can twist it around to make me appear like an enemy. She has tried getting the other girls against me by pulling the whole “depression card” making me look like a bully. My other roommates eventually picked up on her shit and tried getting the random girl living with her kicked out due to our water/electricity going up, we have called the police just to file a complaint about her threatening me, and we went through the apartment office too. She gets really mad when the other roommates speak to me, she is nice to my face but talks major shit behind my back, she is messy, and even threatened to call the police to ruin my birthday. The other day, I forgot my other roommate was throwing a get together for her birthday so I step out of my room just to hear what the noise was. She is right next door too me so as I stand out side for a bit she comes outside (because she is nosey) and then I go back in my room because I didn’t have pants on lol. She will probably come up with something to make it seem like I was spying/plotting towards them or something. I honestly don’t know what to do anymore. My apartment is really nice, a reasonable distance from the campus, and even has a bomb salt water pool! But honestly this girl is so dark sided, childish, and ignorant it brings us down.