I am 56, 126lbs with broad sholuders and longer arms , size 34 A-B, long waisted and the size small fit perfectly.  It is about an inch too long though even with heels.  I plan on hemming it.  I also bought a medium to see the difference and feel its only slightly looser but much longer although it could stretch for a bustier, curvier figure and still fit nicely.  Its very comfortable and low fuss. The waist has a small stretch band with a faux tie.  The tie could easily be removed for a more formal look with a belt.  Although the picture shows a lot of cleavage, it does not and is actually very modest.  Youd have to pull it apart to show more cleavage if thats what you were going for. Overall classy, yet sexy with a pajama comfort!