My wife is a nurse too and we are applying for a visa at the moment. As I see it If your wifes training was not done in Australia she will have to get the skills assessed by the ANMC and pass the IELTS or similar at the required standard. Along with copies of her nurse training certificates she will require a copy of the syllabus used when training, professional references etc the list goes on. Once the skills are assest she will then need to register to practice, as required in the UK, this used to be done with the state you are going to work in but I think it has changed now. All the info is on the ANMC website.
The process is the way it is to stop untrained unqualified people saying they are nurses when they have no formal training