I'd also be getting her to check what her income is listed at in her child support assessment. If she is only on Newstart ($15,500 max with 1 child - I think), and with 50% care, her ongoing payments should be nil. If you have more than 14% care of the child and your income is less than $24500, you won't have to pay anything.
I actually would question if this is accurate information. In a normal circumstance yes, but because he is the non biological father I believe that changes things. My ex husband is currently arguing for 50% custody of my daughter from a previous relationship and I have been advised if he is awarded then her father and I will have to pay him child support as a non-parent carer. She doesn’t have to pay over her CSA obligation but the rates are calculated differently (to my knowledge) in a non-parent carer case.