I ordered a 2X because of the sizing chart, I do not have a small waist, but I am very pleased with this. It has the legging material and it's very comfy. I'm also tall, so I'm always glad things cover my butt.
This dress was the first one I ordered and now I have a couple more. The colors look exactly like the picture. In case it helps you to make a decision, I use S size leggings and M size dresses.