Kerr started the day two strokes behind third-round leader Inbee Park but rallied to end at 16-under-par 272, one shot better than Park and Angela Stanford.
Kerr notched her 15th career win but her first since the 2010 LPGA Championship.
Stanford fired a 4-under 68 Sunday to come close at minus-15, forging a second-place tie with Park (even-par 72).
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