Um..... I'm going to say that I was in a similar situation as OP, many, many years ago. I planned to spay my dog at six months and she got pregnant at four or five months. I was shocked to say the least. I practically never let her out into our fenced city yard unattended for a good three weeks. I never saw a male dog around. Well, surprise! She whelped six puppies if I remember correctly. They all ended up at the local shelter. But she certainly did not bleed to death! Nature does what nature does. Yes, it probably was not good for her, as she was not fully mature. It may have pulled calcium from her bones. But you guys are fear-mongering to say this dog is going to die.
To OP: please follow your heart. Confer with your vet as to how to keep mother and pups healthy and strong. I'm sure you'll all be fine. And please, as soon as your vet recommends, do spay your dear girl.