Career
In 2006, Muller had claimed two freestyle titles (both 400 and 1500 m) under a junior division at the European Championships in Palma de Mallorca, Spain, and at the FINA World Championships in Rio de Janeiro, Brazil, with respective times of 4:15.72 and 16:35.32. After switching from pool to open water events, she wins the 10 kilometer competition at the 2015 world championship in Kazan, Russia. Muller qualified for the 2008 Summer Olympics in Beijing, after placing ninth from the FINA World Open Water Swimming Championships in Seville, Spain.
Muller swam in the first ever women"s 10 km open water marathon, against a field of 24 other competitors.
At the 2011 FINA World Championships in Shanghai, China, Muller edged out United States. swimmer Ashley Twichell to clinch a silver medal by a single tenth margin (01) in the women"s 5 km marathon with a time of 1:00:40.1. Muller also sought to qualify for the 2012 Summer Olympics in London, but missed an A-standard cut (8:3384) in the 800 m freestyle from the national trials in Dunkirk by nearly twelve seconds, clocking at 8:45.55.
Muller was voted 2015 European Open water swimmer of the year by European swimming federation LEN.