i think it will be huge on you. I'm a 6 lately and the small is a bit big on me. Not so big that i can't wear it, but a bit bigger than I would like, especially in the armpits.
Also - maybe its just me but I felt like the ruffles made me look like a house. I think anyone who is maybe bigger than a medium should act with caution.
thanks, gilrs! that looks cute on you, kitty. i found an extra small in the light grey at one of the stores by me; had them hold it but decided not to get it b/c the color is too light for my skin tone and would wash me out - i really wanted the charcoal but oh well.