"I am so proud to join them as major winners at Muirfield," Buhai continued.
"It really is going to be life-changing."
Chun was magnanimous in defeat.
The winner of three majors, including this year's Women's PGA Championship, said: "I never gave up, and gave it may all."
The 27-year-old Korean added: "Ashleigh played a brilliant bunker shot and she deserved it. I am very happy for her."
Buhai had looked in total control when she led by three shots with just four to play.
But she drove into a bunker at the 15th, hit out sideways into rough and then moved the ball just a few yards with her third shot on the way to a triple-bogey seven.
Now tied for the lead, she did well to par the final three holes for a 75 that matched Chun's 10-under par total. The Korean closed with a round of 70.
Japan's Hinako Shibuno, the 2019 winner, finished third on nine under after a final round 71.
American teenager Rose Zhang won the Smyth Salver for the leading amateur. She closed with a 73 for one over par.
Source: AFP
