I have a very small face as well and have a terrible time finding sunglasses. Oakley has good glasses for women, I like the Commit AV for sports.
http://www.oakley.com/women/products/6269 Tifosi also does pretty well on some of theirs. I have these. Or had, because I just found them with a big scratch on the lense :-( They are still a little big but they provide great coverage without making me look like I'm wearing ski goggles.
http://www.tifosioptics.com/...Vogel&niche=WSD/ I just spent a ridiclous amount of money on a pair of Maui Jim's Aviators because I finally found a pair that fit. They were my birthday present to myself and I love them for casual days. I'll never spend this much again on a pair of sunglasses but I've been looking for aviators for a couple years now.
http://www.mauijim.com/baby-beach-4709.html
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Jen "In order to keep a true perspective on one's importance, everyone should have a dog that worships him and a cat that will ignore him." - Dereke Bruce