I cannot tell you the process about applying for a visa.
If you are in a legal and legitimate relationship and you wish to get married the law allows you to do so while she is here in Australia and after the marriage you can apply for her to remain here as your wife and you have to provide evidence of the marriage and the relationship.
Provided this applications is lodged before he tourist visa expires under the law she can remain until the department decides to issue the visa.
Her status will be temporary for a period of 2 years an application to have a permanent visa can be made.
The following link has information about the visa and the requirements and you should also seek the assistance of a migration agent to complete the form and get the application lodged.
The law allows the marriage and for her to stay.
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