She considered that. "Tell me, the date in the Library, was that before or after I was born?" she asked, dryly. "Before or after Demon's Run."

Because the Doctor's reputation went through many changes in the time she's known him. H's been known as he always was, he's been known as a great warrior who could turn armies about at the sound of his name, and he's been scarcely known at all. And he wouldn't have known how grandly his legacy would have changed, given how young he was, in the Library.