I would like to recommend Franklin River Rest Area (VIC) (free), Genoa Rest Area (VIC) (free) and Mystery Bay (NSW) ($12 pppn).....all lovely spots that Ive recently stayed at on my way up the coast from Melbourne. Quiet - no issues as a solo women, highly recommend.
Franklin River - only toilets (no water, no power)
Genoa - only toilets (no drinking water, no power)....many flies as there are cows in the nearby field but not unbearable - fly/mozzie netting makes it ok!
Mystery Bay - long drop toilets, cold showers (no power)