How can a British dental nurse stay permanently in Australia.?

I have residency in Australia because I'm married to an Australian but I want my sister to live here permanently also as does she. She is over on a one year working holiday visa with the option to extend another year if she does three months agricultural work. She is a trained dental nurse and just wondered what her options were. We still have family in the UK so the option of her staying here because I'm her only relative is not an option. Please help, I really don't want her to go back to the UK she is the only blood family apart from my children I have here and although I have my husband and children I'd be quite miserable without her as she would be without me. She is my twin.