Muller, who won the silver medal in the 5 km on Sunday, finished 6 seconds 90/100 behind the new world champion.
"A little frustrated obviously," reacted Muller, who had already had to settle for fourth place with the French relay on Sunday.
"But I'm happy to be at this level after the past two years (...) The goal was to make top 8, so contract completed," she continued.
At 32, the swimmer from Sarreguemines, who has known various fortunes during her career, is coming back from a long absence in the French open water team after changing coach and training location.
Muller was crowned world champion in the 10 km, an event which is on the program of the Olympic Games, in 2015 in Kazan and in 2017, already in Budapest.
At the Worlds-2019, she had experienced terrible disappointment by finishing in 11th place in the 10 km, only one tenth from qualifying for the Tokyo Olympics, despite an appeal on the grounds that she would have been embarrassed by the Italian Rachel Bruni.
In 2016, the Frenchwoman was disqualified from her second place obtained in the 10 km of the Rio Games for having hindered this same Bruni on the finish plate.
The other Tricolore engaged, Caroline Jouisse, took 31st place, 4 min 37 sec 80/100 behind the world champion.
She will also be at the start of the 25 km open water on Thursday.
For Sharon Van Rouwendaal, 28, this is the first world champion title after five world medals in open water and in the pool.
The Dutchwoman, Olympic champion in Rio in 2016 and silver medalist at the Tokyo Olympics last summer, beat German Leonie Beck and Brazilian Anna Marcela Cunha in the sprint after 2 hours 02 min 29 sec and 29/ 100 effort.
© 2022 AFP