Firisia said while the time recorded was far from her personal best she was content with the gold medal.
"I am so happy but not with the time because the heat makes me not perform to the time I want but not far from my personal best," she said.
she clocked 18mins 36 seconds to win gold while her teammate Dianah Matekali clocked a time of 19mins.
Natasha Farrotto of the Regional Australian team claimed bronze with a time of 19mins 21 seconds.
Firisia added that she was already notified of her participation in the Olympics and that the competition is more of a training platform for her and teammate Rosefelo Siosi.
"I am still on my training and I still have three more weeks to go but I am still happy with my performance today.
"We were already pre selected and we know that we are already in the training group for Rio," she said.