Yin, 16, shot a final-round 73 to come from three shots back to take the women's title with a 1-over score of 217, three shots clear of Nicole Gal of Canada.
After opening the tournament with rounds of 69 and 70, Fierro sat at 5-under par entering the final round and had enough of a cushion to hold off a hard-charging Chang who closed with a 71 in very windy conditions to move five spots up the leaderboard into a second-place at 2-over 218. Beni Long of Canada crafted the low round of the day on the men's side with a 4-under 68 to tie for eighth place at 6-over 222.
Yin entered the day three shots off the pace of 36-hole leader Jieming Yang of China. While her countrywomen fell out of contention with a final round 81, Yin was able to snatch the title with a final round 73 which left her at 1-over 217 for her three days of work at El Campeon.
Fierro and Yin are no strangers to the winner's circle.
Fierro, a member of Mexico's Junior National Team, won the Golfweek International Junior tournament a year ago at the Conservatory Course in Palm Coast, Florida, with a final-hole birdie.
Yin, currently the eighth-ranked women's amateur in the world, has won nine times over the last two years. She made history last October with a five-stroke victory in the Zhangjiagang Shuangshan Challenge to become the youngest winner in China LPGA Tour history. She recently finished second to France’s Pauline Roussin-Bouchard at Stage II of LPGA Q-School but did not advance due to her age.