So, you cant apply, she has to apply herself. You can definitely assist her with the application. Being an Indian National, her application will most likely be routed back to India for processing. Try and apply online of she can. Deal with just this trip, one step at a time. Family composition? what do u mean, its not a VV question.
So as you have read the 3 basic conditions are;
Able to show fund in her name for the trip (she can), state self funded and include proof of both bank account and term deposits are in her name and the balances. You should include a letter of invitation and support, stating you will be providing accommodation and most daily living expenses. Make sure she has a return ticket. BUT DO NOT buy tickets until visa is granted.
A Solid compelling reason to leave when her stay is up, use her University enrolment as primary proof here, its a compelling reason.
Demonstrate she is a genuine tourist. Mention you know each other, but 'as friends' you want to show her Australia and tour together. A basic itinerary and plans will help this, and they often question this aspect at the border 'so what are you planning to see when your here'?
Her rejection from Germany as a student will not effect a Tourist Visa application, but she should declare this, as they ask for any visa refusals. Just explain the facts simply.