My 15 y.o daughter really small for her age, should i be worried?

Well you see she turned 15 a few days ago. Shes always been small for her age. She weighs 39 kgs and is 142 cms tall. No bumps or curves or anything. She looks more like a 10 y.o. Alot of the boys thinks shes cute. Should she have grown by now ? No one in my family is that small or from my husbands side either. She definitely doesn't have any problems so is it just that shes naturally like this ?