In October 2007 she made her marathon debut at the Cologne Marathon and won the race with a time of 2:29:33. Mockenhaupt won and qualified for the 2008 Summer Olympics in Beijing. At the Olympic Games she finished thirteenth in the 10,000 metres, in a new personal best time of 31:14.21 minutes. She won the Frankfurt Marathon in October 2008 with a personal best run of 2:26:22. A return to the Cologne event in 2009 brought her a second victory at the competition.