For the price you just can't beat it.  I went with the Small.  I'm 5'5" and bounce between 130 - 135 lbs with a 32 C.  The dress fits great, but getting it off posed a slight struggle.  It's not tight anywhere and I even have wiggle room for weight gain.  Not much, mind you, but there is a wee bit of room for growth.  The part that was tough to wiggle out of is where the waistline meets the bust.  That waist seam is sewn solidly and there's no give when removing the dress.  The old trick of moving it over the hips and stepping out of the dress instead isn't going to fly if your hips are wider than your bust.  I stick with my decision of Small, though.  I didn't want to bump up to a Medium and end up with material bunching or pooching.  If you are at 33 C I'm going to advise bumping to a Medium.

My daughters and mother said the socks were essential to the ensemble so I didn't crop them out of the picture.  Enjoy!