Korda started the day three shots behind overnight leader Choi Na-yeon but fired a sparkling seven under par 66 while the South Korean could only muster a 72 as she fell out of contention.
Lewis also fired a 66 but could not the find the extra birdie that would have forced a play-off and finished the tournament on 18 under.
Korda dropped just one shot in her final round as she went out in 32 and returned in 34 with birdies at 17 and 18 proving vital as she claimed a second LPGA Tour victory.
Lewis was six under after eight holes as she made a charge but a bogey on nine halted her momentum and she could only pick up two further shots on the way home.
Choi finished in the group at 16 under alongside Thailand's Pornanong Phatlum and Americans Paula Creamer and Lizette Salas.
European Solheim Cup stars Sandra Gal and Christel Boeljon both fired 66s to sit a further shot back with P.K. Kongkraphan of Thailand and New Zealand's Lydia Ko also in that group.