“And I’m very fortunate that today was that day.”
Porter’s stunning feat, and a five-under 67 charge from Parisian Laisne, caused jangled nerves for Green.
The West Australian joins the legendary Karrie Webb, Jane Crafter and Jan Stephenson as local Open winners.
Five-time champion Webb’s 2014 title was the most recent for the locals until Green’s emotional victory.
“It’s amazing,” she said.
“I feel really honoured to have my name on that trophy alongside so many great players.”
Australia’s Karis Davidson (six under) tied for fourth as her big-name compatriots and major winners Minjee Lee and Grace Kim struggled.
World No.4 Lee signed for a one-under 71 to finish three over, while Kim made belated ground on Sunday with a five-under 67, finishing three under.
After Porter signed for her course record, Laisne appeared as Green’s chief challenger.
Green and Laisne, who was playing in the group ahead of the local, were tied at 11 under for much of the back nine.
The Parisian was in danger of slipping behind on the par-3 15th hole but managed to save par by chipping in from a precarious down-slope greenside position.
Green made a break on the par-5 16th by holing a clutch 15-foot downhill putt for birdie to create a one-shot buffer.
But she then pulled her tee shot on the 17th into a large fairway bunker.
From an awkward stance, she had a dose of good fortune when her shot from the sand hit a large bunker-side bush but deflected onto the fairway.
Up ahead on the 17th green – with Green sitting on her golf bag looking in the opposite direction – Laisne left a 25-foot par putt short and could only bogey.
Green also couldn’t save par and had another nervy moment on 18: her tee shot sprayed right but, in what she described as a “member’s bounce”, the ball veered from a mound to the fairway.
After Laisne holed a lengthy par putt, the 29-year-old Green also completed a par for a cherished victory.
AAP
