 At the 2007 World Championships she won a bronze medal in the 4×100 m relay, together with teammates Olivia Borlée, Élodie Ouédraogo and Kim Gevaert.With 42.75 seconds the team set a new Belgian record.At the 2008 Summer Olympics Mariën competed in the 4×100 m relay, together with Gevaert, Borlée and Ouédraogo.