She's not only a pro, but a veteran. Only she knows if she's able to perform. If Tom Brady were to tell his coach he didn't think he could go before a game. I think we'd all give him the benefit of the doubt.
As I've said before, she suffered abuse by the US Olympic team doctor and this is the first Olympics after his conviction. It's certainly believable that being at the Olympics has triggered some issues for her.
It's also possible that she quit. We don't know, but as I said above, she has definitely earned the benefit of the doubt.