Altering for skinny child!

My almost 2 yo daughter is size 18-24 months in height, but her weight is within the 12-18 months size. I've been hovering over the Playtime pattern for months, but would really like to know first if it's possible to adjust to make the bodice smaller. I'd like the dress to be more fitted rather than loose, even if it means it won't last long as she grows.