The young Petit was influenced by her maternal aunt who was a follower of Gandhi, and was the Secretary of the Rashtriya Stree Sabha. Petit along with Kasturba Gandhi and Sarojini Naidu played a major part in the Salt March, with Kasturba Gandhi beginning the march at Sabarmati, Sarojini Naidu lifting the salt for the first time at Dandi on 6 April 1930 and Petit standing behind Mahatma Gandhi when he repeated the violation at Bhimrad on 9 April 1930. The march was one of the most important event in the Indian independence movement. In the time when women took a back seat (due to the patriarchal culture at that time in India) Petit was one of the three women who played a pivotal role in the march and the civil disobedience against tax on salt. Petit participated in the Bardoli Satyagraha of 1928 which was a no-tax campaign against the British Raj where she worked under the guidance of Sardar Patel. Petit was instrumental in the anti-liquor movement in India and spent time with Mahatma Gandhi and explained the liquor issue with the schedule tribes in Gujarat.
Petit set up an ashram in Maroli called Kasturba Vanat Shala which taught underprivileged children from families of Adivasis, Harijans and fisher folk spinning, carding, weaving, dairy farming, leather-work and a Diploma Course in Sewing, to make the women self-sufficient. She also opened a hospital of the same name for the treatment of mentally ill patients.
She died on 16 July 1973.