Your girlfriend needs to have an occupation which is currently on the SOL and additionally, be able to meet the minimum requirements for whichever visa that she chooses to apply or an employer who is willing to sponsor her.
Depending on whether you have lived together for a prescribed period of time, she may also qualify for a partner visa - Shel is the resident expert on that front.
Firstly, she needs to identify which visa she wishes to apply for. The DIAC visa wizard will give her an idea of the visa classes that she could possibly qualify for.
Once she has identified the visa that she wishes to apply for, she can visit DIAC's website and understand the requirements/ criteria that need to be satisfied and then take it from there.
It's difficult to give you advice based on the information that you have supplied as there are so many different visas out there but once your girlfriend has figured which visas she qualifies for and the one that she wishes to apply for, then by all means, please do post any additional queries that you may have and we will do our best to provide advice based on our own experiences.
Your girlfriend may also benefit from speaking to a migration agent. Their first consultation is normally free and based on the information she provides, they will be able to give her a realistic view of her chances of securing a visa.