Michelle Wie, who is still searching for her first LPGA Tour win, carded a 2-under 70 and is alone in second at 11-under-par 205. Laura Davies (67) and Se Ri Pak (70) share third place at minus-10.
Women's world No. 1 Annika Sorenstam is alone in eighth place at 7-under-par 209 after a 1-under 71 on Friday at Evian Masters Golf Club.
Defending champion Paula Creamer struggled to a 2-over 74. That dropped her into a share of 11th at minus-4, where she stands alongside Hee-Won Han and Lorie Kane.
Webb took the outright lead with a 5-foot birdie putt on the first. Wie briefly joined her there when she drained a 15-footer for birdie on the third.
The Australian Webb poured in a 30-foot birdie try on the fifth to regain the lead. She moved two clear of the field with a 15-foot birdie putt at seven.
Webb converted back-to-back birdies from the ninth to lead by three at 14 under. However, she lost her drive out of bounds on the 12th and stumbled to a double-bogey.
The 31-year-old found rough off the tee at the 13th and was forced to pitch out. Webb took a bogey there to slide to 11 under, then parred the next four holes while Wie and Ochoa briefly joined her in the lead.
Webb got up and down for birdie from a greenside bunker at the last to end one ahead of Wie.
'I got off to another good start today on the front nine. I was 4 under on the front and then birdied 10,' Webb stated. 'I struggled in the middle of the back nine again. Then I made a really good sand save at the last after hitting a 5-iron into the right greenside bunker.'
After her birdie on the third, Wie fell two back as she parred the next five holes. The young Hawaiian made a 15-foot birdie putt on the ninth, then stumbled to a three-putt bogey on the 12th to slip to minus-10. She birdied the 15th, but hit over the green on 17 and was unable to save par.
Wie hit a pitching-wedge to 18 feet at the par-5 closing hole and two-putted for birdie to remain one behind Webb.
'Well I felt like I played a lot harder than I did the past two days since the wind came up and the pin positions were a lot trickier,' admitted Wie. 'So I feel like I played very smart today and I played very solid. I felt I made putts when I had to, so I feel good for tomorrow.'
Ochoa was 2 under through 15 with two bogeys and four birdies. That gave her a share of the lead, but the Mexican double-bogeyed 17 and bogeyed the last to fall back into a share of fifth place.
Saturday will be the final round, as this event started on Wednesday.