April Pocoruswrote a review of Mountain Hardwear Nitrous Down Jacket - Women's on March 19, 2013
5'1" 120lbs size small.
I also fit an XS in this jacket but returned it for a little extra room for layers. If you're looking for a flattering cut, you may be able to get away with a smaller size, but I think my standard size works best on colder days to have room for a fleece underneath.
Lightweight. Packs into its own pocket. Flattering baffles to accentuate a feminine shape. DWR coating for some water repellency. I feel like this fits exactly as the picture shows, which is rare. Love this down jacket.