Having started the day three strokes off the lead, Yin pumped her fist with satisfaction as she drained a birdie putt on the par-5 18th to finish four-under for the day, before waiting for her competitors to complete their rounds in Springfield, New Jersey.

The 20-year-old finished at eight-under, edging Japan's Yuka Saso (66) by a stroke. Despite finding the rough off the tee at the par-5 18th, Yin reached the green in three and sank a 10-foot birdie putt to break a tie with Saso at seven-under.

"Before today's round, I just told my physio that my goal for today just no three-putts," Yin said.

"I don't care if I'm winning or not – just no three-putts. And I did it, too."

There were no rounds lower than 66 through the first three days of action, but France's Perrine Delacour posted an early 64 on Sunday before Carlota Ciganda of Spain matched that number. Sweden's Anna Nordqvist turned in a 65.

Ciganda, Nordqvist, Northern Ireland's Stephanie Meadow (70), China's Xiyu Lin (67) and American Megan Khang (67) tied for third at six-under.

Grace Kim was the best of the Aussies in 14th. PHOTO: Scott Taetsch/PGA of America via Getty Images.

Grace Kim was the best-placed Australian in 14th at three-under after her two-under-par 69.

Minjee Lee (69) earned a top-20 finish at one-under, with Gabriela Ruffels (72) at even-par, Steph Kyriacou (71) seven-over and Hannah Green (71) eight-over.

In April, Yin became the second Chinese winner in LPGA history, joining Shanshan Feng, when she won the LA Open. Ranked No.25 in the world, Yin began the final round three shots behind Ireland's Leona Maguire, whose 74 opened the door for a host of competitors to make a charge.

Yin started her first 12 holes quietly, with 11 pars and a lone birdie at the par-5 7th, before back-to-back birdies at the 13th and 14th pushed her to seven-under.

"I just told my physio that my goal for today just no three-putts. I don't care if I'm winning or not – just no three-putts. And I did it, too." – Ruoning Yin.

Compatriot Lin, seven years Yin's senior and who is renting her old house in Orlando to Yin, was tied with Yin at seven-under when her tee shot at 18 landed in a water hazard.

Lin wound up with her only bogey of the day and was perhaps the biggest victim of a weather delay that interrupted play for nearly two hours. A storm did not bring lightning but did alter the speed of the greens.

Before the delay, Lin made birdies at Nos.1, 3, 5, 7 and 9, the first three from long range. After the delay, it was all pars until her tough finishing hole.

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"I was in pretty good momentum, and then rain delay made me sit down and maybe have some time to get a little nervous," Lin said.

"I think I did pretty good after I came back out ... all the putts I hit was good. It just didn't really happen."