I've read about more than one person who can run barefooted for miles and live to tell about it. I do think some people have very well-formed and strong feet. Maybe she is also very light in weight. I worked out at first barefooted, doing Karen Voight's Energy Sprint and The Firm. In fact, I did The Firm for years without shoes. Eventually, even though nothing hurt, I got shoes just "to be safe", but for all I know, I've wasted hundreds of dollars!
I always use them for running though, that's for sure. It's those rocks, sweet gum balls, broken glass, roots, dog poop, etc. x(