Jill McGill and Seol An Jeon each posted rounds of 5-under 67 to share second place at 9-under-par 135. Jeong Jang also shot a 67 to move to 8-under-par 136.
Two-time defending champion Annika Sorenstam bogeyed the 17th hole to close a round of 6-under 66. She shares fifth place with Audra Burks (65) at minus-7.
Webb started her round three shots behind overnight leader Tina Barrett. Webb birdied the par-4 second for the second time in two days and came back with a birdie at the fourth at Stonebridge Country Club to move to minus-5.
The Australian came right back with a birdie at the fifth. She parred three holes in a row, then dropped in back-to-back birdies from the ninth to get to 8 under.
Webb however slipped to a three-putt bogey at the 11th. She came right back to birdie the par-3 12th. She converted consecutive birdies from the 14th to climb to 10 under.
She was not done either. Webb faltered to a bogey at the 16th, before closing her round in fine fashion. She drained a birdie at the par-3 17th and came right back to birdie the last to give herself a two-shot edge heading to the final round.
'You have to be patient. Golf's a funny game,' said Webb, who has just one top-10 in her first seven events this year. 'You can be playing poorly and go and win a tournament. You see that a handful of times every year where a person that hasn't been playing that well pops up and wins. I'm pleased with my two rounds, but I've still got a lot of work to do on Sunday.'
McGill notched just one birdie and one bogey over her first seven holes before catching fire. She birdied the eighth, then eagled the par-5 ninth to move to 7 under.
Around the turn, she notched five straight pars. McGill then bogeyed the 15th for the second straight day. She recovered with an eagle at the 16th and birdied the 17th to share second place.
Jeon opened with a bogey at the first, but bounced back to run off four consecutive birdies from the second to get to 7 under. She moved to 9 under with birdies at the eighth and 10th. The Korean bogeyed No. 11. Jeon closed out her round with a birdie at 17 to move into a tie for second place.
'My driver's a little shaky, but still my irons were good,' Jeon said. 'I missed a lot of putts, but I still shot 67. So I feel really comfortable with this course and this condition.'
Sorenstam started at minus-1, five shots of the pace. She birdied three of the first four holes to vault up the leaderboard.
After seven straight pars, the Swede ran off four consecutive birdies from the 12th to get to 8 under. The top player in the women's game dropped a shot at the 17th to fall four strokes behind Webb.
'Yes, it was revenge from Friday. I thought I hit the ball pretty good then, I just really couldn't put it together,' said Sorenstam, who will also defend her title at the McDonald's LPGA Championship next week. 'I wasn't in between clubs as much in this round and also hit it a little closer to make the putts. That was the big difference today.'
The cut line fell at even-par 144 with 74 players moving on to the final round. Among those who missed the cut were Suzann Pettersen (145), Laura Davies (145) and Sophie Gustafson (147).