Can you share the story of how Udi helped Khimji Lalji Joshi's very ill daughter?

Certainly. Chapter 33 recounts a story noted by R. Hari Sitaram Dixit about Khimji Lalji Joshi's daughter. She was so ill and weak that she could not walk, and her limbs had become as thin as twigs. Her mother first sought Baba's Udi, which provided some immediate relief. The family then traveled to Shirdi, where the girl had to be carried to see Maharaj. As detailed in the chapter, Baba personally applied Udi to her and blessed her. Remarkably, within two to four days, she began to walk on her own. When she still had some difficulty getting up, Baba gave her a fruit to eat, which resolved the final issue.