What should my dad do?

My mum is a horrible person, she always lies about everything. And I mean everything. Makes up stories and has made my dads life a living hell for years. She does not work and hasn't for years. She went out and signed up for a business which my dad had to try and bail her out but ended up losing his car because of it. They have been separated for a few years but he still pays all the bills for her as she says because the business is classified as investment she can't get anything from centrelink. She is now claiming he needs to pay her a deserted wife payment and refusing to get a divorce when he applies for one.
Then she finds out dad has met a lady who he is just friends with she gets another crazy lady to drive her to his workplace an hour away and assaulted him.
I want nothing to do with her as she is beyond help and crazy, how can we get this crazy lady out of our lives. Please
She has also starting driving past my house, I have children so I will call the police if this continues. How can a mother be like this?