For reference- 5’3, about 130lbs, 34C, usually a US size 4/small/27 or 28 in denim depending on the brand.
Also really enjoying this piece, especially the color. I first got the Amiel in the charcoal gray color and tried both the S and XS. I prefer the XS on me, the small would look a bit too oversized. Both very comfy, versatile pieces.