Koivumaki qualified for the women's half-lightweight class (57 kg) at the 2008 Summer Olympics in Beijing, by placing fifth from the 2007 World Judo Championships in Rio de Janeiro, Brazil. She reached only into the second preliminary round, where she lost by two yukos to China's Xu Yan. Because her opponent advanced further into the semi-finals, Koivumaki offered another shot for the bronze medal by defeating Algeria's Lila Latrous, with a koka and a golden score, in the first repechage bout. Unfortunately, she finished only in ninth place, after losing out the second repechage bout to Japan's Aiko Sato, who successfully scored an ippon and a yoko shiho gatame (seven mat holds), in three minutes.