So. You here yet? [EDIT: two weeks time, I see. Do please let us know how you find things!]
Things to look out for:
a touch of Dutch cafe , in Berwick. Outskirts of Melbourne, but they have a bunch of Dutch food and books, should you feel homesick.
I may have accidentally translated Het Wilhelmus into Klingon for the owners…
I can’t better the comprehensive responses from my betters, that you got to see in time for your planning. There would have been an extra culture shock for your girlfriend if she’d spent more time in NZ—Australia is just that bit bigger and brasher for her to be taken aback; but if she left at 5, she’s culturally Dutch. (And no shortage of Kiwis here, anyway.)
EDIT: Ah, just remembered the biggest downside for my German friends that have moved here.
Melbourne has a bedtime. Exceedingly hard to find anyplace open past 11, other than a few nightclubs and bars you don’t want to be in. It has not really had an all-night culture, although there are active moves to remedy that (including all-night public transport.)