Ruby Rox Semi-Formal/cocktail strapless dress

Strapless dress from the early 2000s, great condition! Red rose attached on the lapel, red tulle to fill out the skirt. Zip up the back, material is slightly stretchy. Tag says size 11, I'm not quite sure how that translates to today's sizing. Waist: 15.5" Across the top: 13.5" but this part is very stretchy to hold the strapless dress up. There is absolutely bust allowance. When I wore this years ago, it fit me fine and I'm an A. My sister had worn it more recently and she's at least a C