Demut won her first national title at the German Athletics Championships 2003 and set a personal best of 13.74 m that year for fifth place at the 2003 European Athletics U23 Championships. She achieved a jump of 13.96 m in Stuttgart in February 2004 and had consecutive runner-up placings at the German Indoor Championships in 2004 and 2005. A quiet 2006 season for her was highlighted by an outdoor best jump of 13.96 m. She cleared the fourteen-metre mark for the first time the following year and claimed the national title both outdoors and indoors. Demut won the German outdoor title again in 2008 and placed sixth at the European Cup.