Easson’s side led 12-0 at the break in Whangarei thanks to a score from hooker Lana Skeldon and a penalty try.
But Australia – who finished with 13 players after Ashley Marsters and Adiana Talakai were sent off in the closing stages – scored 14 second-half unanswered points to seal a dramatic victory.
“It was always going to be tough,” Easson told ITV. “We knew the wind was really strong first half and we probably could have done with another few points.
“We knew Australia were going to pressure us. We had to keep the ball and build phases, but it just wasn’t to be that second half.”
They now have to beat New Zealand next Saturday to keep alive hopes of staying in the competition.
Easson said: “These guys are so close, it was the same against Wales. They’re playing some good rugby.
“You see the passion that’s in them, the fight that they give. I feel heartbroken for everybody because of the work that they’ve put in.”