Can you tell me the story of the woman who came to Shirdi with a plan to fast for three days?

Certainly. As recounted in Chapter 32, a woman named Mrs. Gokhale came to Shirdi with a letter from Kelkar. She had made a firm resolve in her mind to fast for three days at Sai Baba's feet. This intention was in direct opposition to Baba's philosophy, which held that one should eat first before attempting spiritual contemplation. Being omniscient, Baba was already aware of her plan before she even arrived. He had previously told Dada Kelkar, "In this Shimga (Holi) festival, will my children remain hungry? How can I let them remain so?" This demonstrated both his foreknowledge and his fundamental disagreement with the practice of fasting for his devotees.