Free People Mini Dress Brown Layered Drawstring Waist 3/4 Sleeves Size XS/S

Size XS or S?

Measurements lying flat (double where appropriate):
Armpit to armpit: 16"
Sleeve from shoulder: 16"
Waist: 15"
Hips: 18"
Shoulder to hem: 31"

Very excellent condition.  No holes or stains.  Tag size hard to see.  Use measurements.