Maria Hjorth moved into a share of second place at 6-under-par 138 after a second-round 70. She was joined there by first-round leader Becky Morgan, who struggled to a 2-over 74.
Paula Creamer is alone in fourth place at minus-5 after a 68. Mi Hyun Kim, who shared second place here last year, is one stroke further back at 4-under-par 140.
Ochoa opened with bogey on the first after her second shot came up short of the green. She knocked a wedge to 3 feet to set up birdie at the third.
The Mexican pitched her third to 6 feet for birdie on the par-5 eighth. Ochoa two-putted for birdie from 50 feet out at the par-5 11th to move to seven-under.
Ochoa, a two-time winner in 2004, rolled in a 12-foot birdie putt at the 16th before closing with a pair of pars at Locust Hill Country Club.
'I'm very pleased with my run today,' said Ochoa. 'I don't know how I shot better yesterday than today, because today I hit my driver better. I'm very happy with my 8 under and looking forward to tomorrow for a sunny day and get a couple of good rounds.'
Hjorth opened with a 4-foot birdie putt on the 10th. She then ran home a 30-foot birdie try on the 13th. The Swede faltered to a bogey on the 16th, but came right back with a birdie on 17 to get to 6 under.
The 31-year-old, who won twice in 1999, drove into the trees on the first and that led to a bogey. Hjorth rebounded with a 6-foot birdie putt on the sixth to get back to minus-6.
'I started off ten and hit a very good second shot into there and made the putt and started off with a birdie,' Hjorth said. 'It's always nice to start off with a birdie, especially when you played well the day before and then I just played really solid. Overall, I'm very pleased with my round and I've got it going together and I had a lot of birdie chances that I didn't make.'
Morgan ran off five straight pars to open her round. She then drained a 25- footer for birdie on the sixth to move to minus-9. The Wales native tripped to a bogey on No. 10.
The 30-year-old erased that error by draining a 20-foot birdie putt on the 11th. She closed with three straight bogeys to tumble out of the lead.
Gloria Park and Se Ri Pak share sixth place at 3-under-oar 141. Laura Davies, the 2001 champion, posted her second straight round of 1-under 71. She stands in a tie for eighth at 2-under-par 142 alongside Jenny Rosales and 2003 U.S. Women's Open champion Hilary Lunke.
Kim Saiki, the defending champion, managed an even-par 72 on Friday. She stands in a tie for 24th at 1-over-par 145.
The cut line fell at 5-over-par 149 with 76 players moving on to the weekend.