On July 31, 1971, she set a world record in Lübeck with Ellen Tittel, Sylvia Schenk, and Hildegard Falck in the 800 meter relay. Merten started the 1500 meter run at the 1972 Summer Olympics and the 800 meter run at the 1971 European Athletics Championships, but failed to reach the finals. She won the silver medal with the relay in the 2000m medley relay with Elfgard Schittenhelm, and with a time of 5:01.1 minutes at the 1970 European Athletics Indoor Championships. At the 1972 European Athletics Indoor Championships, she earned fourth place at the 800 meter dash.