Lee, of Australia, had a three-shot lead in the final round over Harrigay, having smashed the 23-year-old’s record of 54 holes with a shot of 67 on Saturday.
The tournament was held at the Pine Needles Golf Club in South Pines, North Carolina – the fourth time the venue has hosted the event.
The 26-year-old got the last round for a perfect start with a comfortable birdie on the first hole, followed by another on the second where she was draining 30 feet.
Lee wiggled a little in the 5th and 7th holes while making a bogey, but she regained her composure to track those bugs with four pars and a birdie.
After 12 holes, he was the fourth golfer in the world to be six shots off the course and from there sprint towards the Harton S Simple Cup.
Lee’s younger brother and fellow pro golfer Min Woo Lee took to Twitter on Sunday to congratulate his sister.
“This hits hard. Tears in my eyes,” he wrote on Twitter. “Very proud. Just a baby girl from Perth. Two big wins in her name now.”
“Alcohol enthusiast. Twitter ninja. Tv lover. Falls down a lot. Hipster-friendly coffee geek.”