Gulbis started the day four behind Inkster and had birdies at the first, sixth and ninth. Out in 33, she was 5 under and shared the lead with Shin.
Also in the hunt at the halfway point were former top-ranked Annika Sorenstam, Gustafson and Inkster, who all made the turn at 4 under.
Gulbis, who won $450,000, gave part of the credit for her win to a back injury two months ago that forced her to take a month off and make some adjustments.
"I had to change my golf swing because of my injury," she said. "I was kind of thinking this might be a blessing in disguise."
Wie pulled her opening shot out of bounds and started with a double-bogey 6. She had bogeys at the third, sixth and seventh and a birdie at the fifth where she holed a huge putt of about 70 feet to go out in 40. The teenager then battled back with a level par second nine of 36.
"I kept my head together," Wie said. "It all came down to today and there were a couple of stupid errors out there. I just have to keep the ball in play and use my head more and be patient with myself."
Recovering from a wrist injury, Wie was pleased with the round.
"I kept my head on today. I was very proud of myself," she said.