Canadian coverage just touted it, as the European fellow above said, as "Top American Gymnast Backs Out Of Competition, Citing Mental Health Issues", and that's as far as it went.
In reading a few articles and the statements she gave, and watching the competition after the fact, it does seem she was more scared of hurting her legacy, and maybe where that would leave her psychologically afterwards, than actually being mentally broken and unable to compete.
Also, it really shows a bit of entitlement as an American athlete, to be able to quit. Imagine if a Chinese or Russian athlete fell off the beam and just said "Nope, I'm done." They don't have that privilege, so it wouldn't even cross their mind. Not that that's a good thing, per say, but it's a very different mindset and perspective. Simone's fortunate to be able to quit without serious backlash, let alone be praised for it.
Regardless, she was fun to watch so I wish her the best. Might be time to hang up the leotard competitively though.