I suggest that this is simply an example of supination, where when walking the foot tends to lean outwards, thus giving the 'bow-legged' effect. A high thin heel will amplify if not cause this, as it introduces an element of instability that is scarcely present when walking nearly flat-footed. I experience this myself, especially if walking in a heel that is thin and/or higher than about 4". But even in 'normal' footwear, my shoe heels wear more on the outsides. My understanding is that a degree of supination is very common; its opposite (pronation) much less so. Our legs part much more readily than they move together (as any woman is aware!).