Yes, adding your spouse (or life partner) as another driver to your rental car is permitted in Australia.
Please note that car rental companies such as Avis, Budget and Hertz do not charge the Spouse of the Lead Driver (of any gender) as an additional driver when you pick your vehicle.
Apart from the main driver's spouse, you may also add the following people as additional drivers for free:
Read more about Adding Another Driver to Your Car Hire in Australia.