Creamer had control at Cedar Ridge until a bogey on the 18th hole for the third straight day gave her a 1-over 72. Inkster poured in an 18-foot birdie putt for a 70 to force a playoff for the second straight year.
They finished at 2-under 282.
Creamer, who lost in a playoff last week to Annika Sorenstam, missed a 12-foot birdie putt for the win on the first extra hole, but made from 8 feet on the next hole, No. 10, to avoid what would have been a devastating loss.
Inkster, 47, was trying to become the oldest winner on the LPGA Tour. She also lost in a playoff last year at Cedar Ridge.
Ochoa, trying to tie the LPGA Tour record with her fifth straight win, started the final round eight shots behind and never got it going. She closed with a 69 and tied for fifth, five shots behind.