In 1989 came the highlight of Arendt's career as she won the gold medal at the World Indoor Championships. She finished ahead of American Diane Dixon, who had finished fifth at the Olympics, with a margin of 0.25 seconds. At the 1990 European Championships, however, Arendt was again knocked out before the final round of the 400 metres competition, only reaching the semi-final. She finished fourth in the 4 x 400 metres relay with teammates Karin Janke, Andrea Thomas and Silke Knoll.