You are not required to put down a fathers name on the birth certificate in Victoria.
But not putting down a name also means no child support.
If your friend intends to collect a parenting payment then she only needs to declare that she is unsure who the father is. Unless things have changed over the last few years of course. My girlfriend was in a similar situation a few years back in Victoria. She collected Parenting payment and was made exempt for collecting child support and was given an allowance of sorts to compensate for the lack of child support. I don't know how much though.
She did tell centerlink that she didn't know who the possable fathers names were at the time. And I'm sure thats why she was made exempt.