I would suggest ordering her usual size as our fitting can be quite generous. The Small (8-9yrs) measures 35 inches around the chest, 22.5 inches in length and the sleeves are 27 inches long. The medium (10-12 yrs) is 38 inches around the chest, 24.25 inches in length and the sleeve is 29.75 inches long.
Please note the sleeve is measured from the back of the neck, over the shoulder and down the outside of the arm.
Answered on 11/3/2015 by Claire from Lands' End