Regarded during the 1980s as the fastest female runner on the Asian continent, she won gold in the 100-meter dash events at the New Delhi Asiad of 1982 and the Seoul Asiad of 1986 and went on to win the same event at three Southeast Asian Games (in 1987,'91, and '93) and two Asian Athletics Championships.
Early in her career, she swept the 200 and 400-meter races at the SEA Games of 1981.
She competed in the 1984 and 1988 Olympic Games. After retiring as an athlete, she became a Singapore-based school sports coach.
A native of Meycauayan, Bulacan, Philippines, she is the daughter of Francisco De Vega, who also served as her athletic coach. Her marriage to Paolo Mercado resulted in three children, including a son, John Michael, who died tragically at the age of four.
De Vega and English athlete Angela Bailey both competed in short-distance running events at the 1984 Summer Olympics.