My hamster is small for her age?

Ok so i got a hamster and it had 5 babies and ate 3 (same old same old hamsters eat their babies). So i have the mother hamster (snooki) and the two baby hamsters (cookie wich is my sisters and franny wich is mine.) The babies are about 9 months old (september 1st). Cookie is about the size of snooki. But franny is small. Like smaller than cookie. About the size of a 5 month old hamster. She has an exercize wheel food water and plenty of toys. So does the other hamsters. They are in seprate cages because they are syrian hamsters. Is it because shes just naturally small? or because of the genes? or wuld have she been the one that wasnt going to survive and just did? I dont want any silly stupid answers. Im kind of scared for her. Please give an answer soon.