I don't know if me being a father can be much help since I just buy my daugther stuff that fits her,cause I don't really look at the size. As for as size it says 26.I'm used to the small,med,large sizes.But the dress is way longer than 26 inches.So it can't be over all length,I'm thinking the waist area.
It probably would fit my daughter,because she wear's the same size as her mom.But it was my wife's,and my daughter doesn't want the dress.I believe my daughter is a 7-8.I hope that info helps.