
When my bitches get very sore mouths from cleaning pups they totally ignore dry food.
As others have said, she needs to eat a huge amount to rear her litter. I always buy steak mince, chicken breast, and white fish. You can poach the white fish in goats milk for her, and try scrambled eggs. She may need feeding in the whelping box, it's quite normal to hand feed bitches after whelping to get them to eat enough.
I would suggest that you feed on demand once you get her on wet food. It's surprising how much they can get through.