Can we quickly review the shoes that we think she may have worn and how they relate to what was found??
I believe you have identified 3 different pairs of shoes that she had with her during the flight, 2 blucher oxfords and the lighter soled shoes. identified in previous reports as pairs 1, 2 and 3.
pair 1 is a non capped blucher oxford. I have not seen a good image of the bottom of this shoe to view the sole. I would like to see more images of this shoe. it appears more well used than others from what I could tell.

pair 2 has a toe cap. it is easily identifiable in almost every picture because the heal of the shoe is divided down the middle lengthwise into different colors. the instep being much lighter.


pair 3 is completely different, lighter and more ornate.

It has been verified that she is about a size 6.5 by measuring a known set of shoes she had purchased for herself.
general "shoe related information" (modern era, not sure how this applies to 1940)
for american sizing, women's shoe sizing in general is 1.5-2 sizes larger numerically than a mans shoe of the same size. ie a mens 7 is equal to a women's 8.5-9
british shoes seem to use the same or similar size between mens and womens shoes.
a womens shoe in general is narrower than a mans for the same size(length).
US mens sizing and british sizing are different by one shoe size. An American size 6.5 shoe would be a 5.5 in british sizing.
a size 10 shoe as described by galaghar, would equate to a men's size 11 in the US. that would be an extremely large shoe for a woman. my only other though would be that it was possibly very narrow?? with both men's and women's shoe parts being described things get a little fuzzy and hard to pin down. nothing is ever easy. given the bones measurements I think we can assume that the american size 11 shoe was not owned originally by the castaway.
as far as other ways a shoe could have gotten there it's pretty endless. the kiwi's being there for a couple months wrote about wearing out shoes constantly. not surprisingly the coral, sand and salt were all very rough on footwear.
most of the norwich crew kicked off their shoes to swim ashore. very possible they washed ashore.
I don't recall reading much about the bushnell crew and shoes... although I'm sure they went through them as well given the time they spent not only on this island but others. possible that they also had items to maintain them as well, such as replacement heels?? what type of shoes I wouldn't have much knowledge.
as far as I have read or seen in pictures the natives did not wear shoes. if this was a castaway it would certainly not be a native wearing the shoes, but a non-native COULD pick up a discarded worn out shoe from wherever it could be found in a trash pile near an old campsite to make do.