Nigel, I agree that Clementine is described as light, and the shoe size mentioned, if original, seems to be meant to illustrate that fact.

However, at the particular incident, she was not wearing any shoes of any regular size specification, either because she no longer had any (- worn them through back in '49 -), or because the weather was too warm and sticky after all that rain. Rather, she wore makeshift sandals, good enough for shuffling around the tent, but not to walk near that crumbly canyon edge.

Women never have enough shoes ...