LZed

I am an Australian, and I am currently organizing my Girlfriends 417 Visa (looking at checking out Aus for a few months to see if we want to settle and then will progress to the partner visa if we decide to stay). My question - they are asking for a statement proving $5000 in sufficient funds. My girlfriend does not have this. However, my father who is an Australian and currently living in Australia is happy to provide these funds.. he doesn't want to transfer into her account (we'd lose a lot in International transfer fees and poor exchange rates) but he is happy to sign anything or write an affidavit stating he will provide any funds if needed? Is this possible or are they strict on having the actual funds within the applicants account? Thanks in advance!