She changed nationality from Nigeria to Spain in April 2007, following in the footsteps of another hurdler Glory Alozie. Her first medal as a Spaniard came at the 2007 IAAF World Athletics Final, where she took the hurdles silver medal. She started the following season with a gold medal at the 2008 European Athletics Indoor Cup, but tripped at the last hurdle at the 2008 IAAF World Indoor Championships and finished in last place. Onyia set a Spanish national record at the 2008 IAAF Golden League meet in ISTAF Berlin meeting, recording 12.50 seconds and improving upon her previous best by 14 hundredths of a second. She competed in the hurdles at the Summer Olympics and just missed the final after finishing fifth in the semi-finals. In 2016, she was disqualified from the 2008 Olympics for doping, and her result was annulled after her 2008 sample was re-tested and failed.