I chose a medium size (M) for my size 6 baby so I have extra fabric to turn into a Merida hunting dress. I fully expected to have to hem it, but while I had enough work to hem it above her ankles, the rest suited her slim figure. So I would suggest trying it on, especially if you don't want a tight fit. For the price it worked great and she loves it. Although the arms were two very different sizes (length and width): I may not have noticed it only on her, but it was very noticeable where I took the dress apart and put it back together.
Rainbow Toddler Princess Sleeveless Sundress Girls' Clothing and Dresses
57 Review
Amazon Brand Sleeveless Unicorns Metallic Girls' Clothing in Dresses
75 Review
UNACOO 2 Pack Sleeveless Cotton Dresses Girls' Clothing
62 Review
Fancy Girls Communion Dresses White Girls' Clothing in Dresses
53 Review