From what I observed to my hedgie, each day they gain 1gram if no exercise. You said when you got her she was with her mom and 3 brothers right?When they're 2 months old, the male is available for breeding already and they're not picky with their mate. That's why in lots of breeders, it's already common sense, when they see the male gets aggressive they should separate the male already because they might try to mate with their sisters or mother. That's the disadvantage of petshops because they don't know the what's right and wrong because they just sell, they're just advised by the breeder, and just sell accessories. Only few petshops are knowledgeable.
If your 3month old hedgie is pregnant there would only be a slight chance of her giving birth safe. No one can tell if she's going to live when she give birth.