Overnight leader Chun In Gee doubled her advantage to two strokes after a second-round 66 lifted her to 13 under at the Evian Championship in France.
The South Korean had shared top spot with Park Sung Hyung in the final major of the year but her compatriot dropped back after a 68, while American Annie Park's two-over 73 saw her fall from one off the lead to eight adrift.
Chun's nearest challenger is China's Olympic bronze medallist Shanshan Feng, last year's Order of Merit winner and currently third in the rankings, who shot a 67.
Defending champion and world number one Lydia Ko carded a 68 to move to four under and tied for 13th.
Two-time major winner Britanny Lincicome matched Chun's best-of-the-day 66 in a mixed round of nine birdies and four bogeys.
The American, starting from the 10th, opened up with two bogeys to leave her one under for the tournament but then responded with a remarkable run of eight birdies in nine holes from the 13th.
Her run came to an end when she bogeyed the par-five fourth but a birdie-par-bogey finish saw her close five shots off the lead on eight under.
Source: PA
