
Did you get her checked after you thought she'd finished whelping? I am concerned that this not wanting to eat could be because she has retained birthing material or even a dead puppy and has infection building up. Obviously if she had a Section (?) that should have all been removed, but if not, then unless you are experienced, I'd always get a vet to check her, confirm empty and also check the puppies for any abnormality you might have missed.
Next how many puppies does she have to cater for because with a small number she may well know she has enough nourishment to cater for them. And newborn puppies don't take much from mums in any case - and it is just colostrum initially.
Why is she being given puppy food? She should be on her normal good quality food, plus perhaps with some extras like raw mince, cottage cheese, scrambled egg and so on (not all in the same meal!). Puppy food may be way too rich for her at this moment. We've never used this for our lactating bitches in any case.
The point about how many placenta she was allowed to eat is a good one - she may quite simply not be hungry!!