Kyriacou finished with the shot of the day, a fairway metal on the par-5 18th that rolled in for an albatross, giving her a 67 to tie for sixth place at 16 under, 10 shots behind the winner.
The Australian's closing 67 followed rounds of 71, 68 and 66.
Compatriot Grace Kim also finished in the top 10, taking out ninth place at 15 under after rounds of 67, 70, 72 and 66.
Another Australian, Robyn Choi, tied for 20th, carding rounds of 71, 70, 70 and a brilliant 65 to be at 12 under.
Ryu closed with an eight-under 64 to finish at 26 under. She became the second player to go wire-to-wire on the LPGA Tour this year.
It was also her second time winning a new event, after taking out the FM Championship at the TPC Boston last year.
She was coming off a rough finish at the Chevron Championship last week, sharing the 54-hole lead at the first major of the year until closing with a 76.
This one was closer than the five-shot margin indicated. Ryu was clinging to a one-shot lead over Germany's Esther Henseleit going to the back nine. She missed a six-foot birdie putt on the 10th - her third straight miss from short range for birdie.
But then she made a 15-foot birdie putt at the 11th, and an eagle at the 13th put her ahead by four shots.
"Incredible day," said Ryu, who now has won in each of the past seven years dating back to her first win as an 18-year-old on the Korea LPGA.
Henseleit, who started three shots behind, went out in 31 to get within one shot. She cooled on the back nine, not making another birdie until the 18th hole for a 66. She tied for second with China's Ruoning Yin (67).
"Started out great on the front nine and then couldn't quite keep up on the back," Henseleit said. "Haeran played amazing and she really deserved to win it today."
Yin, who got back into the mix with a 62 in the third round, was four shots behind at the turn. She ran off four straight birdies starting at the 11th, all of them inside eight feet. The last one got her to within three shots of Ryu.
The South Korean responded with an approach into three feet on the 15th for a birdie to restore her lead to four shots, and Yin fell back with a double-bogey from the bunker on the 16th.
Another Chinese player, Yan Liu, closed with a 65 to finish alone in fourth.
Ryu is the 10th winner in 10 tournaments on the LPGA Tour this season.
