If she's suckling puppies and she suddenly won't eat she does need to be seen by a vet pretty urgently. It is possible she could have eclampsia. Of course it could be some other thing wrong, but she will need all the nutrition she can get while she is nursing pups
But...how long ago were they born? If only a number of hours or a day or two, then her not wanting to eat is quite normal. Immediately following birth, many dogs refuse to eat, sometimes for a day or so.
she may have a bone or a piece of food lodged in her throat take her to a vet to get her checked out.