Complex sentence: Pandit was a harsh critic of her niece, Indira Gandhi, after Gandhi became Prime Minister in 1966, and she retired from active politics after relations between them soured On retiring she moved to Dehradun in the Doon Valley in the Himalayan foothills.
Split into simpler sentences: Pandit was a harsh critic of her niece, Indira Gandhi, after Gandhi became Prime Minister in 1966, and she retired from active politics after relations soured between them. Upon retiring, she moved to Dehradun in the Doon Valley in the Himalayan foothills.