Thank you for all your replies.
I would like to let you all know that my partner and I took our chances and applied for registration of our relationship in Victoria even though her civil partnership with her ex has not been officially dissolved..and good news! Our application has been approved and we are now registered as a couple in Victoria! My partner just had to provide evidence of termination of her previous relationship (which only needs to list the date that the relationship officially ended). In short, a relationship can already be registered here in Australia even if one partner was married or in a civil partnership and the marriage/civil partnership has not been officially dissolved, as long as you can provide proof that the previous relationship has ended. :)