Co-medalists Angel Yin and Jennifer Hahn dropped out of the U.S. Women's Amateur on Wednesday, losing first-round matches at Portland Golf Club.

France's Justine Dreher beat the 16-year-old Yin, from Arcadia, California, 5 and 4. Vanessa Ha of Plano, Texas, topped Hahn, the 21-year-old Vanderbilt player from Henderson, Nevada, 4 and 3.

The 23-year-old Dreher, the oldest player to advance to the round of 42, won four of the last five holes on the front nine to open a 5-up lead and finished off Yin with a birdie for a halve on No. 14.

"I putted really, really well," said Dreher, coming off her senior season at South Carolina. "I didn't miss any 10-footer or less besides hole No. 3, and I had a lot of them."

The 19-year-old Ha, a rising sophomore at San Francisco, won four straight holes on the front nine to take a 4-up lead. Hahn twice pulled within three holes before falling with a halve on the 15th.

"I was focusing mostly on my mental game, and that's the biggest indicator for my putting," Ha said. "The key was that I wasn't focusing on trying to make the birdies. They just went in."

Dreher and Ha survived a playoff Wednesday morning to reach match play.

Defending champion Kristen Gillman of Austin, Texas, advanced with a 2-up victory over Kelly Su of Scottsdale, Arizona. The 17-year-old Gillman won last year at Nassau Country Club in New York.

Hannah O'Sullivan of Chandler, Arizona, routed Haley Mills of Tyler, Texas, 7 and 6. The 17-year-old Sullivan won the Symetra Tour's Gateway Classic in February in Mesa, Arizona, at 16 to become the youngest winner in the history of the professional circuit.

Eun Jeong Seong, the 15-year-old South Korean player who won the U.S. Girls' Junior last month in Tulsa, Oklahoma, beat Duke's Celine Boutier of France 1 up.

Mariel Galdiano, the 17-year-old from Pearl City, Hawaii, who won the Canadian Women's Amateur last month, topped Kimberly Mitchell of Woodbridge, Virginia, 7 and 5.

Elizabeth Wang of San Marino, California, beat Stanford star Mariah Stackhouse of Riverdale, Georgia, 1 up. Stackhouse three-putted the final hole for a bogey.