The United States' Brittany Lincicome carded a six-under 65 to move into the lead at The Evian Championship in France on Friday.
Kim Hyo-joo had set the pace with a record-breaking round of 61 on Thursday, but failed to deliver a repeat performance as she posted a score of one over par on Friday.
Lincicome registered six birdies in a faultless second round that lifted her to 10 under, a stroke clear of Kim and three ahead of Hur Mi-jung, who managed a second round of 69.
Norway's Suzann Pettersen is the leading European at six under, level with Karrie Webb after the Australian followed her opening 65 with a 71.
Ryu So-yeon was one under at the end of day one, but saw her tournament come to an end on the second day of action.
The South Korean was disqualified for tapping in on the fourth after bending the shaft of her putter.
Australia's Minjee Lee enjoyed a better day as she shot a round of 67 to move into contention on her professional debut.
The 18-year-old now sits at three under par - seven shots adrift of the lead.
"My putting really helped today," she said. "I wasn't hitting it that close, but I think my putting really saved me.
"Yesterday there was a bit of nerves, but today was much better.
"I feel like it [being a professional] should be different, but I feel really comfortable and like I belong here."