2004 started for Groot with the 2004 European Aquatics Championships in Madrid where she achieved to win three medals, silver in the 4×100 m freestyle alongside Inge Dekker, Annabel Kosten and Marleen Veldhuis. There was a bronze medal in the 50 m butterfly and another bronze in the 4×100 m medley together with Stefanie Luiken, Madelon Baans and Marleen Veldhuis. After this tournament she prepared to compete at the 2004 Summer Olympics in Athens, Greece, where she was on the team that captured the bronze medal in the 4×100 m freestyle relay, alongside Inge de Bruijn, Marleen Veldhuis, and Inge Dekker.