What breed of hamster is it? It is possible for that to happen. The cage might be to complicated and when the female/male got stuck somewhere and their partner might step of them will cause a fight. It happens to my winter white before but i manage to reintroduced them back after 1month.

You already did the wrong thing by buying her a female and a male hamster. They will breed and keep on breeding till the female die from malnutrition or the male die from fighting with the defensive pregnant female because the male wanted to mate with the female. Also winter white are territorial hamster and you're suppose to keep 1 per tank/cage. There is always stress to hamster when there is another hamster in their territory.

Unless the winter white are siblings and have been kept together since young. Then there is a chance of keeping them together but remember same sex pair to keep them from breeding or in-breeding.