The New Zealander began the ultimate spherical in a share of fourth however made three birdies over a flawless first 14 holes to problem for the title, which boiled all the way down to an exciting finale between Ko, Nelly Korda and Lilia Vu tied on the high of the leaderboard on six beneath par.
Ko took the clubhouse lead with a superb birdie on the 18th, however defending champion Vu was nonetheless on her heels proper to the tip.
Vu wanted a birdie to power a play-off, however ran up a bogey 5 to safe victory for Ko.
A 3rd main title caps off a improbable couple of weeks for Ko after she took Olympic gold earlier this month.
Talking on the trophy presentation, Ko – who had recorded 11 top-10 finishes at majors since her final win on the Chevron Championship eight years in the past -said: “It’s fairly surreal. Successful the gold medal in Paris a few weeks in the past, it was virtually too good to be true.
“Clearly heading into the weekend I used to be in rivalry, I mentioned ‘how is it attainable for me to win the AIG Girls’s Open?’ I’ve had probably the most Cinderella-like story this previous few weeks and that is virtually too good to be true.
“To be holding this trophy proper now, I can’t imagine it and it’s clearly very particular this yr with my household being right here this week too.”
This yr’s occasion noticed golfers competing in some robust winds, however Ko insisted she loved her expertise over the Outdated Course regardless of some tough climate circumstances.
“I feel I simply had a whole lot of enjoyable and it was virtually so windy that I hit some pictures and all I may do was snort as a result of I’ve by no means seen a ball react that manner,” she added.
“It was tough however going into the week I feel all of us gamers knew it was going to be powerful on the market, that’s why it’s an enormous spherical of applause to the workforce right here, the superintendents for making the course playable as a result of it was so windy that it may’ve simply not been that case.
“I’m winded out, however I’ve truly bought a golf journey subsequent weekend and it’s meant to be windy there too so no less than I’m prepared for subsequent week too!”
Vu’s dropped shot on the final noticed her end on 5 beneath and in a tie for second with Jiyai Shin, Ruoning Yin and Korda.
Victory slipped away for world primary Korda after she hit the ball into the Highway Gap bunker on the seventeenth, which she subsequently bogeyed.
England’s Charley Hull endured a irritating closing day and finally completed tied for twentieth on one over par.
England’s Lottie Woad received the Smyth Salver, awarded to the main novice after a closing birdie gave her a one-under-par whole.