Reigning U.S. Women's Amateur champion Kimberly Kim and Ha-Na Jang of South Korea each shot 69 on the 6,094-yard layout at Kearney Hill Golf Links.
Korean Wonjoo Choi shot 70. Kate Ackerson, of Allen, Texas; Marci Turner, of Tompkinsville, Ky.; and Ryann O'Toole, of San Clemente, Calif., finished with 71s.
Defending champion Tiffany Joh opened with a 74, as did NCAA Division I player of the year Amanda Blumenherst. Blumenherst led Duke to its third consecutive national title last month.
Lua is a two-time winner on the American Junior Golf Association circuit and a junior-to-be at Los Altos High in Hacienda Heights, Calif.
She hit 15 greens in regulation, and two of her five birdies were tap-ins. She did hole a 25-footer at 17 and the other two were from 10 feet.
'Probably the difference between this year and last year is I've been working out to try and get stronger,' said Lua, competing in her seventh USGA event. 'I've actually gained a club (of distance) and a couple of more yards with my driver. I average 220 to 230. It's not too far, but it's better than it was before.'
Stroke-play qualifying continues with 18 holes on Tuesday, with the low 64 scorers advancing to match play, which starts on Wednesday. The 36-hole final is scheduled for Saturday.
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