Alfredsson, who won her first LPGA event earlier this year at the Nabisco Dinah Shore, had seven birdies, including a 20ft putt on the 17th, to recover after a bogey and a double-bogey had reduced her to par.
Okamoto played a more consistent round. After a bogey at the eighth, she came back with birdies at the 14th and 15th holes.
Dawn Coe-Jones, of Canada, was three under on 69. Although holding par on the 16th and 17th, she drove into the pond at the 18th and finished with a bogey.