I've always been a bit obsessed with hair. I used to cut my dolls' hair and as soon as I was old enough, I was perming, frying, colouring and extending my own locks. Hair is an important transforming feature, as far as I'm concerned.
It made me laugh, then, when I got my second MS back from a professional reader. Your main character seems obsessed with her hair, the reader wrote. At one point, she's so engrossed she says she's entranced by her new hair-cut.
Well, who wouldn't be entranced by a killer cut revealing beautiful cheekbones and sparkling eyes, I thought (yes, it was just that bad of a novel).
So maybe I used a bit (a lot) of overkill in that scene, but I still think a character's physical changes can certainly be used to reflect internal changes.
What about you? Do you use changes externally to reflect characters' internal change?