No dependant's visa. Common law wives are not recognised under HK law. She will have to enter on a tourist entry stamp and travel out of HK to renew it every 90 days. Working would be near impossible. However, I notice form your profile you may be from Aus, If your girlfriend is an Aussie or a Kiwi, she can apply for a 1 year temporary working visa. Exemptions for those nations exist.