Lewis had five birdies and two bogeys in the second round for a 36-hole total of 12-under 132. Ariya Jutanugarn turned in the round of the day with a bogey-free 66 and pulled into second place at 9-under for the tournament.
Beatriz Recari and Ryu So-yeon each shot 4-under 68 and Catriona Matthew had a 69, leaving those three players tied for third at 8-under.
Jutanugarn was 2-under through 11 holes Friday. She jumped into second with three birdies over Nos. 12-15 and another at the 18th hole.
Lewis had birdies at the first and sixth holes but bogeyed the ninth. She followed that with back-to-back birdies to open the second nine in getting to 12-under for the tournament. Lewis had a bogey at 14 but returned to 12-under with a birdie at the next hole.