yes, your wife can apply for Hong Kong Entry Permit at Consulate General of China in Melbourne, you can travel to Hong Kong by ferry from Guangzhou, please bear in mind that if you travel on this itinerary Australia-Guangzhou-Hong Kong - Nanning, you need a double entry visa because you enter Mainland China for 2 times, Hk and Mainland China apply different exit & enter rules, from Guangzhou to Hk means exit Mainland China.