Hi, I assume that they have not divorced or reached a binding property settlement.
The only way to sort out the financial settlement side is to reach a BFA - Binding Financial Agreement outside of Court (this MUST be done with the assistance of their own lawyers advising them before they sign, and providing them with a certificate to this effect), OR by Court orders with or without consent (that is they both agree, and ask for the Court to approve the orders, or they cannot agree and the Court decides what orders to make).
Without a binding property settlement or Court orders, she cannot force him to do anything with respect to the car payments, etc... I assume there is also Super, and potentially other assets, and debts that need to be sorted out.. generally the sooner the better.
Please pass this prescribed reading issued by the Court to her:
She can enlist the help of the Child Support Agency to help assess and collect child support.