I need my MIL GONE

All she does is cause us problems and drama. Me and my husband rarely argued until she moved in with us 2 years ago. She is disabled and couldn't really afford to go somewhere else, even though she always threatens to when she's upset with us. Now she wants to get mad at us for arguing when she is the cause of it 95% of the time. She always has her earbuds in and NEVER hears us when we are actually talking to her, but it never fails that she will complain when we argue. I'm sorry, but arguments are normal in a relationship, nobody is going to get along 100% of the time. She has also started arguments with my dad(we used to rent from him) and completely ruined mine and his relationship. I need her out of my house NOW. However, she contributes $500 for rent, that we would have to figure out how to come up with, and I can't work because I'm pregnant with twins, and when I'm not pregnant, if I got a job it would probably only pay for childcare because we will have three kids. How do I make $500 a month so I can get this woman out of my house next time she threatens to leave???