Low blood sugar can be a sign of diabetes.. . It could also mean when she's older, she has more chances of having a stroke than others with normal blood sugar.. . Low blood sugar means that your little sister doesn't have enough (good, healthy) sugar in her system.. Maybe you should like... take her to the convenience store and let her buy a lot of candy :P. Actually, that's kinda dangerous.. . Ask your doctor if it is a sign of diabetes and he will tell you everything you need to know.