EVIAN, September 14, 2013 (AFP) - Already a victor in four events playing alongside the professionals -- she retained the Canadian Open on the LPGA Tour just last month -- Ko added a 67 to her opening 68 and was tied for second on seven under par, one behind Japan's Mika Miyazato, with 18 holes to play.
The teenager had four birdies in an unblemished card to finish alongside World No.3 Suzann Pettersen, yet she was still frustrated not to go lower.
"I did chip in for par at one hole but I left so many putts out there," she said. "It was building up inside and I was getting pretty angry."
But she remained patient and it paid off as she finished in glorious style at the 17th and 18th.
Miyazato, the Japanese player with just one professional victory to her name, shot a second round 69 to retain her one shot lead in the weather hit Championship.
Park Inbee, the world No.1 who won the first three majors this season, had a 71 to set alongside her first round 74 and was outside the top 50 on three over par and just one inside the cut.
Sweden's heroic Solheim Cup player Caroline Hedwall looked as if she might miss the final round at seven over par after 11 holes. But she covered the last seven in a spectacular seven under par, including a hole in one at the 16th. Back in 31 for 68 she finished on even par.
In its first year as a major, the Championship has been reduced to 54-holes due to a catalogue of weather problems. Heavy rain earlier in the week resulted in Thursday's play being washed out and with more torrential downpours forecast for overnight and Sunday, there is even a chance it could extend into next week.
Miyazato, whose good friend but unrelated namesake, Ai Miyazato, twice won the event in its previous form as the Evian Masters, made a shaky start to her second round played in glorious sunshine.
She bogeyed the first two holes came back with birdies at the sixth and seventh.
She also birdied the 13th before saving the best for last on her eight under round. At the treacherous par four 438 yard 18th she hit her second shot with a hybrid three wood to a couple of feet and knocked it in.
"It is tough just to make it to the green," she said. "So the birdie at the last was definitely the highlight of my round."
While delighted at the prospect of maybe becoming a major champion, the 24-year-old admitted that she was disappointed that the outcome will be decided over three rounds.
"I'm not happy," she said of the decision. "A major should be 72 holes."
Pettersen has won a major - the 2007 LPGA Championship - and the world No.3 is seeking back-to-back wins following her triumph two weeks ago in the LPGA Safeway Classic. She is also still riding high from Europe's Solheim Cup victory in Colorado last month.
If Ko does win she would join 1967 US Women's Open Champion, France's Catherine Lacoste, as amateur winners of women's majors.
Michelle Wie was a 15-year-old when she finished runner-up to Paula Creamer in the 2005 Evian Masters.
Leading second round scores at the Evian Championship USLPGA golf tournament on Saturday:
134 - Mika Miyazato (JAP) 65 69
135 - Suzann Pettersen (NOR) 66 69, Lydia Ko (NZL) 68 67*
136 - Stacy Lewis (USA) 69 67
137 - Choi Chella (KOR) 70 67, Ryu So Yeon (KOR) 71 66, Pak Se Ri (KOR) 66 71
138 - Kim In-Kyung (KOR) 69 69, Beatriz Recari (SPA) 69 69, Lindsey Wright (AUS) 68 70
139 - Vicky Hurst (USA) 71 68, Paula Creamer (USA) 70 69, Lexi Thompson (USA) 72 67
140 - Momoko Ueda (JAP) 70 70, Michelle Wie (USA) 68 72, Karrie Webb (AUS) 68 72, Christina Kim (USA) 67 73, Jennifer Johnson (USA) 70 70, Angela Stanford (USA) 69 71, Sandra Gal (GER) 66 74
141 - Holly Clyburn (GBR) 71 70, Rebecca Lee-Bentham (CAN) 75 66, Azahara Munoz (SPA) 70 71, Lee Ilhee (KOR) 70 71, Lizette Salas (USA) 70 71, Han Hee-Won (KOR) 69 72
142 - Juli Inkster (USA) 74 68, Anna Nordqvist (SWE) 74 68, Katherine Hull-Kirk (AUS) 71 71, Caroline Masson (GER) 70 72, Feng Shanshan (CHI) 70 72, Morgan Pressel (USA) 70 72, Ayako Uehara (JAP) 69 73, Choi Na Yeon (KOR) 69 73, Danah Bordner (USA) 69 73, Caroline Hedwall (SWE) 74 68
* - denotes amateur