Worms cause damage to the intestines and to the stomach- it takes time for that damage to heal. She would not improve the same day if the issue was worms.
But I would think that if she is not eating, you have more than worms although that maybe what started it. The other things people asked would help to have an idea of what's going on.
Also how is her eye lid and mouth color? Is she pale? If so she may need iron supplements.