About 200 meters into the race in Eugene, Oregon, the 22-year-old tripped and finished last. She was running in the middle of the pack.
The winner, Nia Akins, will be going to Paris with Allie Wilson, who came in second, and Juliette Whittaker, who finished third.
As a youngster, Mu was projected to be a major rival of Team GB’s Keely Hodgkinson, who finished second in the 800m in Tokyo to the American.
After the final turn, Quincy Hall overtook 2022 world champion Michael Norman in the men’s 400-meter race, winning in 44.14 seconds.
Norman remarked, “I know I can run far faster than I did.
“It was just a poorly executed race; I got a little too excited during the moment, so I paid for it at the end.”
Sixth place finisher Quincy Wilson, 16, is in the running to be called up to the relay pool, while third place finisher Chris Bailey will represent his country in Paris.
In the men’s 110-meter hurdles, Grant Holloway won his heat and went on to win silver at Tokyo 2020.
“I just wanted to put pressure on the field, let everybody know that I’m still on top,” Holloway stated.