Kersee telling the world Athing may not run world's is exactly what a coach should NOT do with a race shy athlete. It's very clear Mu was very nervous and afraid to lose this year. Understandable, the pressure is high.
Then your coach says that you may not even show, putting a spotlight on her lack of excitement to compete and leading to a ton of (justified) criticism.
The correct way to handle this was to have her run a few low key races, easy wins to nuild confidence. Give her 1 big race to test herself then go to worlds.
If you are afraid of something, hiding from it won't take the fear away. Facing your fear will.