She had the self-assurance that comes with being young and believing that you can do anything, combined with the fact that you simply can’t consider consequences that far reaching at that age.
It seems that when Emma Watson first went out for the role of Hermione she never bothered to ask herself whether or not she was capable of doing the job.
However, now the actress gets asked whether or not she thinks she can do things, like carry a musical, which forces her to confront the same question.
She was jumping in with both feet into a film franchise that was clearly going to change her life in some way, though apparently, she didn’t have the “awareness” of that at the time.