Chidori,
Typically 2008 Fall runs small... however, it somewhat is random... yikes!
Plus, some dresses run big in the hip but small in the bust, vice versa, etc.
Also, since I'm lucky enough to be near a boutique, I've noticed that the same design in the same size can fit different! I actually have photos, come to think of it.... Like one wrinkles a tad bit at the waist, but I don't think most people can see the difference (I'm picky). These dresses are hand done! That said, they usually are gorgeous either way.
Anyway, since they are stretchy, most in xs and xxs will work. Hope that helped? Also, sales associates can let you know when you call about a specific dress.
I'm usually happy with either xs or xxs in the same style. I'm about the same size as you.
Gorgeous gorgeous dresses. Girls will ask you where you got it every time you go out. Good luck!