Free People Boho Mini Floral Dress

EUC Free People Deep-v-neck floral slip fit & flare dress in black / pink / purple / green & raindrop back. Size says XS. This is the first time I noticed that... I normally wear M-L and this fit, except it was a bit too short for me... perhaps the size explains it. I guess for a looser fit and decent length, S or XS would be the right sizing, but this fits a M or L easily (given a cup size less than a C).