Guegan made her official debut for the 2008 Summer Olympics in Beijing, where she competed in the women's 800 metres. She ran in the third heat of the event, against six other athletes, including Kenya's Pamela Jelimo, who eventually became an Olympic champion in the final. She came only in third place by nine hundredths of a second (0.09) behind Jamaica's Kenia Sinclair, with a time of 2:03.85. Guegan advanced into the next round of the competition, as she secured the final mandatory qualifying slot in the third heat. Guegan, however, fell short in her bid for the final, as she did not finish the race in the third heat of the semifinal rounds.