The 14-year-old Son from Eagle Canyon began her last trip around Golf Du Bassin Blue in a tie for the lead with tournament favourite and defending champion, Jade Rousseau.
After a disappointing 77 in the second round, Son finished as she started, with a one-over-par 73.
The South African had 15 pars at the tight layout and offset bogeys at the sixth and 12th holes with a lone birdie at the par-five 14th.
“It was definitely a better day for me with the short game and the putter,” said Son. “I did miss a few short ones, but anytime you make par at this course, you feel like you’ve made a birdie.
“The locals were not kidding when they said you have to get to know the course. It’s incredibly tight and anything that goes even slightly off-line is punished.
“Jade was having the sort of day I had in the second round on the front nine, but she rallied hard to finish second. This course has been a real learning experience and is has been an adventure I will treasure for a long time to come.”
Van Wyk, a fellow scholar at Curro Aurora, began his final round three strokes behind former professional Franck Michel and one shot ahead of Bassin Bleu’s Johan Mouniama.
The Ernie Els and Fancourt Foundation golfer cancelled a bogey start with a birdie at the third and had a bogey-birdie combination at the sixth and seventh holes. He dropped two shots at the ninth and turned two over.
Van Wyk dropped shots at the 12th, 14th and 16th to sign for a 77 and a share of joint second with Mouniama. The pair finished six strokes behind Michel – the runner-up in 2014 – who closed with a 74 to claim a popular home victory.