Dresses differ
I tried this on in a different retailer a couple of weeks ago... ....tried on a different one last night..same size and it looked baggy, sleeves way too long, etc.  let me add that i am usually a xs/s petite but some regular extra smalls will work also.  this was a xs reg.  even the sa could see that one looked like it fit smaller ( i showed her the photo in my phone) while this one swallowed me.  bottom line, you will need to try this one on as the sizes seem to vary.