I conjecture they didn't let her fly because they thought it was a fake passport. Imagine if you gave the TSA a passport that says you are "female." They will confiscate the passport and probably take you to a room for questioning to ask why you have a false passport.
This has nothing to do with a track meet. It's about people leaving the country with fake passports. Hers might be real with a mistake on it. But that's a huge mistake.
So, as you know from flying internationally, they check your picture, name, date of birth, and sex really quickly. If something doesn't pass the smelling test they look closer.
This. It's also her first passport so probably some clerk made a mistake in the processing.