"Today I felt that my driver was really solid. Obviously my irons weren't good so I just have too keep it together. It's like a puzzle. I'm just getting one bit at time."
Ochoa saw an opportunity of a three-shot lead slip to one with a bogey at the last.
She went to the 18th green with a two-shot lead and faced a 25-foot putt for birdie. Her first putt, hit too strongly, curled four feet past the hole and then she missed that to wind up with a bogey 5.
She also missed a putt for eagle at 14 but her 6-under 140 puts her one ahead with Wendy Ward (70) and Catriona Matthew (68) tied for second.
"It was a good day. I'm pleased with my round," the Mexican said. "I'm upset about the 3-putt on 18 but I'm just glad I still have the lead.
"I'm very pleased the way we worked the strategy with my caddie. I think we are in good shape and we understand pretty good the golf course and hopefully we can keep doing the same thing for a couple more days."