Born to Surama Devi and Pramada Ranjan Ray (who was the younger brother of Upendra Kishor Ray Choudhuri), Leela spent her childhood days at Shillong, where she studied at the Loreto Convent. Surama Devi had been adopted by Upendra Kishor Ray Choudhuri . Lila’s grandfather had left his younger two daughters in care of his friends after his wife died. The eldest daughter was sent to a boarding house. Her maternal grandfather was Ramkumar Bhattacharya, who later became a sannyasi and was christened Ramananda Bharati. He was the first among Indians to visit Kailash and Mansarovar and wrote a travelogue Himaranya. In 1919, her father was transferred to Calcutta, and she joined St. John’s Diocesan School from where she completed her matriculation examination. She ranked second among the girls in the matriculation examinations in 1924. She stood first in English (literature) both in her honours (graduation) and Master of Arts examination at the University of Calcutta. The family she belonged to made a notable contribution towards children’s literature.Sunil Gangopadhyay says that while the Tagore family enthused everybody with drama, songs and literature for adults, the Ray Chaudhuri family took charge of laying the foundations of children’s literature in Bengali.
She joined Maharani Girls’ School at Darjeeling as a teacher in 1931. On an invitation from Rabindranath Tagore she went and joined the school at Santiniketan, but she stayed only for about one year. She joined the women’s section of Asutosh College in Calcutta but again did not continue for long. Thereafter, she spent most of her time as a writer. After two decades as a writer, she joined All India Radio as a producer and worked for about seven-eight years.
Her first story, Lakkhi chhele, was published in Sandesh in 1922. It was also illustrated by her. The children’s magazine in Bengali was founded by her uncle, Upendrakishore Ray Chaudhuri in 1913 and was later edited by her cousin Sukumar Ray for sometime after the death of Upendrakishore in 1915. Together with her nephew Satyajit Ray and her cousin Nalini Das, she edited and wrote for Sandesh throughout her active writing life. Until 1994 she played an active role in the publication of the magazine.