PNG won the game in the first half, scoring all three of their goals through Georgina Kaikas, Ramona Padio and Meagen Gunemba.
Gunemba, after three games, has scored five goals.
PNG will meet New Caledonia for gold this Thursday. New Caledonia was too strong, beating Cook Islands 5-1 in the first semi-final earlier today.
This means Cook Islands play Samoa in the bronze play off.