Representing Seychelles at the 1999 All-Africa Games, Joanna competed in the women's 100 metres, 200 metres and long jump. Although she failed to win a medal in any of these events, she was selected to take part in the Sydney Olympics the following year, running in the women's 100 metres: Hoareau finished sixth in heat seven of the qualifications with a time of 12.01 seconds and did not progress to the semi-finals.