She finished 2nd at the Kenyan cross-country championships in 1991 behind Tegla Loroupe. Chepngeno was selected to compete at the 1991 IAAF World Cross Country Championships in Antwerp, Belgium, but finished only 46th. She finished 15th at the World Cross Country Championships held in Boston, United States of America and was part of the Kenyan gold-medal winning team
She started her career while at Kitopen Primary School. Later she suffered from injuries and was not able to repeat her earlier success. She was still competing in 1999.
During her running career, she was a corporal in the Kenya Prisons, which is famous for recruiting promising Kenyan athletes.
Before starting running, she took High jump and javelin throw. She keeps a 5-acre (20,000 m2) plot in Kitopen bought with her prize money.
She is not married, but has two sons, one of them was four years old in 1994.
In 1992 she won the Kenyan trails for the 1992 IAAF World Cross Country Championships. She did not make the Kenyan team for the 1993 IAAF World Cross Country Championships, but won a bronze medal at the 1993 African Championships The 1994 World Cross Country Championships were held in Budapest, Hungary where she became the first Kenyan woman to win individual World Cross Country Championships gold medal. She remained the only Kenyan national to win the long race at the World Cross Country Championships, until 2009 when Florence Kiplagat won the race.
