Sarah Huarte, second-round co-leader, closed with a 1-under 70 to take second place at minus-six. Seul Ki Kim shot even-par 71 on Sunday to grab third place 4-under-par 209.
Kelly Lagedrost, who shared the lead with Huarte entering Sunday's play, struggled to a 2-over 73. She finished in a tie for fourth at 3-under- par 210. She was joined there by Lisa Ferrero and Charlotte Mayorkas.
Choi got her round going with a birdie on the second. The Korean picked up back-to-back birdies from the ninth to get to 7 under. She picked up another birdie on 16, but closed with a bogey on the par-5 18th to win by one stroke.
Cristina Baena carded the low round of the day as she fired a 4-under 67 to move into a tie for seventh at 2-under-par 211. She ended alongside Annie Young and Sarah-Jane Kenyon. Mayumi Nakajima, Stella Lee and In-Bee Park were one stroke further back at minus-1.