Biles withdrew from the competition because she was unable to perform. She was not making a political statement. She was not fighting for mental health rights. She failed her vault, realized she didn't have it that day, and withdrew.
Conservatives have been using sports to fight the culture war for generations. Black athletes have been using sports to make political statements for generations. This was only one of those things. It wasn't revolutionary because Biles was making a sport decision for the best outcome of the team.
She is not prioritizing her health and safety. If she were doing so she would have retired after 2016, a champion and a millionaire. Being a world class athlete is bad for your health. This is all post hoc justification for her having a bad night and pulling herself from competition, which was a justifiable action if she felt she couldn't perform considering USA gymnastics has a great team and could still win the gold without her.
The olympics is not "just another day on the job" for Simone Biles, that's you and your spin, promoting the issues and framing you think are important. Did you even watch the event? When I take a day off work, I'm not in tears. Biles was devastated. Pulling herself from the event was indeed a rational decision. I'd characterize it as mature and selfless because it wasn't for her health or safety. It was because on that day, in her judgement, the three other american women had a better chance to win gold without her.