At the 2010 French Championship, in Saint-Raphäel, she wins both the 200 m individual medley event and the 400 m individual medley event, finishing second to Coralie Balmy in the 200 m freestyle event. At the European Championships in Budapest, Muffat arrived as the favourite to take gold at the 200 m individual medley, declaring to the press that the gold medal is her objective in that event. However, after leading the field into the third discipline of the medley, the breaststroke, she was overtaken by Hungarian Katinka Hosszú, causing Muffat to lose momentum and finish fourth in the event. On the same day, the French 4 × 200 m freestyle relay team also finishes second in the final when Muffat, who was anchoring the French relay, got overtaken by another Hungarian swimmer, Evelyn Verrasztó. Two days later, she would also finish 4th in the 200 m freestyle event, which was won by Italian swimmer Federica Pellegrini.