What is the story of the old woman who fasted to get a mantra from Sai Baba?

The story, recounted in Chapter 18, is about an elderly Deshmukhin with extreme faith who came to Shirdi. She made a firm resolve to receive a secret mantra directly from Sai Baba's mouth, considering any other source impure. To achieve this, she undertook a 'dharna' (fasting protest), renouncing all food and water. For three days and nights, she persisted in her fast, becoming exhausted but remaining steadfast in her goal, even willing to fast unto death. Her plight worried Madhavrao (Shama), who went to Baba to plead on her behalf, describing her stubborn resolve and warning of the potential scandal if she were to perish.