If any of ours wants to eat, we let them eat, its natures way & its instinctive in some to eat it as if they were in the wild, the placenta would attract predators. Its a good source of nutrient for the bitch. Some bitches will not entertain it & will sever the pup from the placenta & ignore it( the placenta not the pup LOL), some bitches have just looked at the pup in the bag & wondered what to do next & give you a look of disbelief if you offer the placenta to them to eat!
We've had one bitch eat some & leave others.