Katherine Hull posted her best career finish, taking second place at 8-under-par 280 after a closing 69. Leta Lindley fired a 68 on Sunday to jump into a tie for third place at minus-7. She was joined there by Il Mi Chung and Angela Stanford.
Janice Moodie, who led after each of the first three rounds, struggled to a final-round, 3-over 75. She dropped into a tie for sixth place at 6-under-par 282.
Lee started her round at minus-6, three strokes behind Moodie at Glen Arbour Golf Course. The Korean parred her first six holes, while Moodie was falling back to the field.
The 23-year-old Lee drained a birdie putt on the par-3 seventh. After a pair of pars, she sank another birdie putt on the 10th to move to minus-8.
Lee jumped into the lead at 10-under as she birdied Nos. 12 and 13. However, she fell back to the field with bogeys on her next two holes. Lee then birdied the par-4 16th for the third straight round to climb back to minus-9.
She parred her last two holes, then watched as no one in the final two groups could match her total. Lee's win came on her first full season on tour.
Moodie was joined at minus-6 by Johanna Head and Brittany Lang, who recently turned pro. Emily Bastel closed with an even-par 72 to finish alone in 10th place at 5-under-par 283.
Meg Mallon, the 2004 champion, finished with a 3-under 69, her first round in the 60s all week, to end in a tie for 16th at minus-3.
Lorie Kane and Dawn Coe-Jones tied as the low Canadian finishers at 1-over- par 289.