Lee outlasted Caroline Hedwall, winning by three shots over the Swede with Koreans Haeji Kang and Inbee Park and American Brittany Lang tied for 3rd.
For Lee it was her second win of the season and with another runner-up finish to boot she may yet challenge Lydio Ko for the Louise Suggs Rolex Rookie of the Year title.
Joint third round leader and world number one Stacy Lewis faded surprisingly with a final round of 75 and eventually finished tied for 6th.
Sarah Kemp finished 45th and Sarah Jane Smith 58th.
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