One of my bitches was spayed during an emergency c section, one of the puppies was so lodged in her pelvis, her uterus tore at the cervix when they tried to dislodge him. She went on to have plenty of milk for her babies, they were fat and healthy puppies before I started feeding them. Sometimes milk can come in a little slower, (with a spay at c section, and it is Not recommended to spay at the time of a c section) but with some medications, and food supplements they can give to stimulate milk production, and keeping puppies on her, it is *usually* not a problem.
Maybe this poor girl's injuries shocked her system somehow, so she is fighting to survive, rather than produce milk.