"I've only heard of it a time or two. And then they don't... they don't remember being here." Then there's the Doctor's theory. That the ones who were here are dead. The replacements might come from different universes, or from earlier in their timelines, but..

She can't imagine the Doctor getting out of his own volition and not taking more people. Or, at the very least, gloating a little in proving so many people wrong - he was her friend, but she had a sense of his ego.