Alex shot a closing five-under 66 to win by a shot from World No.1 Jin Young Ko (66) at 10-under at hilly and windy Palos Verdes Golf Club on Sunday.

American Meghan Khang (68) and World No.3 Lydia Ko (70) of New Zealand tied third one shot further back.

A one-shot overnight leader after enjoying a three-stroke second-round lead, Australia's Hannah Green slipped to a tie for fifth, three shots behind Alex, after mixing four bogeys with her three birdies in a final round 72.

Countrywoman Minjee Lee started the final day tied third but fell to a tie for 13th after a 71 with three bogeys.

After starting the final day in the lead, Hannah Green was unable to secure a third LPGA Tour win. PHOTO: Harry How/Getty Images.

Fellow Australian Sarah Kemp also started the day with some chance to win from four shots back but carded a 73 to be tied 26th.

Alex, 31, won for only the second time, adding to her 2018 Portland Classic title.

"The hard work has paid off," said Alex, who recently fought a herniated disk in her lower back. "I wasn't sure if this would ever happen again if I'm being perfectly honest. It's been tough.

"We're all getting older. I'm getting older. There are so many amazing players out here. The competition is really, really difficult.

"So, I just didn't know if my mind and body were going to put me back in a position that I was going to be able to do it again. Today was the day."