I never saw the movie, but your situation makes me think of "The Princess and the Warrior" for some reason.

She sounds tough, though, since she can walk in heels for any distance without discomfort. I love how my legs look in heels, but when I've got them on I might as well have my husband carry me around.

If she can function, and most importantly: run, in heels, then you can't really help what's on her feet since you can't logically fit shoes in her purse. You're probably fighting a losing battle trying to get her to reconsider her footwear.

A decent first aid kit small enough to fit in her purse would be a better notion. Band-aids and moleskin would probably be a great help.