What should I do?

My brothers girlfriend recently started living at our house. She never asked if she could, she just asked if it bothered them. My parents are way too nice, so they said sure. At first, she was cool. Lately, she's been getting on my nerves. She invites herself and HER family to my family's get togethers. She is EXTREMELY lazy. All she does is eat, watch movies, use her phone, and lock herself in my brother's s room. My 2 year old niece even started saying, "fuck, shit, and bitch because of her. I'm tired of it. My brother has broken up with her multiple times, but she refuses to leave him. He's kicked her out 3 times, and she still won't leave. HELP!