Can you tell me the story about how Udi helped the daughter of Khimji Lalji Joshi?

Yes, Chapter 33 of the Shri Sai Satcharita recounts the story of Khimji Lalji Joshi's daughter, as noted by R. Hari Sitaram Dixit. The girl was severely ill and had become so weak that her limbs were like twigs and she could not walk. Her mother first obtained some of Maharaj's Udi, which provided immediate relief. The family then traveled to Shirdi, where the girl was carried to Baba. As detailed in the chapter, Maharaj applied Udi to her and blessed her. Within a few days, she began to walk on her own. When she still had trouble getting up, she complained to Maharaj, who then gave her a fruit to eat, which completely resolved her remaining difficulty.