I went through a similar experience years ago. You will have to write a letter of demand to her, I'd also send it to her insurer, but ultimately you may end up in the small claims court. I'm pretty sure the following link should get you pointed in the right direction.
http://www.legalaid.wa.gov.au/Inform...Insurance.aspx
Sadly, even though the probability is that she will be ordered to pay, it's likely that she will suddenly have no assets, no income, and the court will do nothing.