Daughter of Dasaundha Singh Gill, was married to Gurbakhsh Singh, son of jai Singh, leader of the Kanhaiya clan. As the menace of Ahmad Shah Durrani's incursions receded, conflicts broke out among the Sikh misl chiefs. Mahan Singh Sukkarchakkia, helped by Jassa Singh Ramgarhia and Sarisar Chand Katoch, attacked Jai Singh in 1785.

A fierce battle took place at Achal, about 6 km south of Batala, which was the seat of the Kanhaiyas. Jai Singh was defeated and his son, Gurbakhsh Singh, husband of Sada Kaur, was killed. The bereaved, yet farsighted, widowed Sada Kaur, persuaded her father-in-law, Jai Singh, to offer the hand of her only daughter, Mahitab Kaur, to Ranjit Singh, the five-year old son of Mahan Singh Sukkarchakkia. The marriage came off in 1796. Sada Kaur accompanied her daughter to Gujranwala after the nuptials. She became one of the members of the triune regency for young Ranjit Singh who had succeeded to the leadership of the Sukkarchakkias upon the death of his father in 1792. The other two members were Mai Raj Kaur (popularly known as Mai Malvain), mother of Ranjit Singh, and Diwan Lakhpat Rai, his minister. Mai Malvain and Lakhpat Rai were removed from the scene by death, the latter having been killed in an expedition against the warlike Chatthas. Sada Kaur was now the only one of the triumvirate left to guide and counsel Ranjit Singh. Being by now head of the Kanhaiya misl, she provided him with material help as well. She helped him to occupy Lahore defeating the Bharrgi chiefs, Mohar Singh, Sahib Singh and Chet Singh, from whose misrule the citizens had sought the Sukkarchakkia Sardar to rescue them. Lahore fell to the joint command of Ranjit Singh and Sada Kaur on 7 July 1799. Supported by his mother-in-law, Ranjit Singh made further acquisitions and assumed the title of Maharaja on 11 April 1801.

In the campaigns of Amritsar, Chiniot, Kasur and Kangra as well as in his expeditions against the turbulent Pathans of Hazara and Attock, Sada Kaur led the armies side by side with Ranjit Singh. But both were strong personalities and mutual clashes began to occur. The marriage of Sada Kaur's daughter to Ranjit Singh did not prove a happy one. Mahitab Kaur's first son, Ishar Singh, died in infancy. On his return from the Sutlej campaign in 1807, Ranjit Singh was presented by Sada Kaur with twin sons, Sher Singh and Tara Singh, born to her daughter, Mahitab Kaur. But Ranjit Singh had already married a second time and the son born to this union was acknowledged as the heir apparent. This soured the relations between the mother-in-law and the son-in-law. Sada Kaur now opened secret negotiations with Sir Charles Metcalfe and Sir David Ochterlony to secure herself the status of an independent Maharani. She further offended the Maharaja by not attending the heir apparent's marriage in 1812. She did not allow even her grandsons, Sher Singh and Tara Sirigh, to join the ceremonies. Ranjit Singh started making inroads into the Kanhaiya territory lying on the other side of the River Beas.

The breaking point finally came when on Sher Singh's attaining majority, Ranjit Singh insisted that Sada Kaur hand over the administration of her estates to him. Sada Kaur refused and threatened to seek the protection of the British in the Sutlej territory and hand over to them the town of Vadhni, located to the south of Sutlej which Ranjit Singh had conquered and transferred to her in 1808. The Maharaja cajoled Sada Kaur into visiting Lahore, where she was kept under strict surveillance. Once she managed to escape in a covered litter, but was detected and brought back. Her territory was, in the meantime, sequestered and the wealth of the Kanhaiyas lying at Atalgarh (Mukeriari) was confiscated. Batala was granted as a jagir to Sher Singh while the rest of Sada Kaur's estates were placed under the governorship of Sardar Desa Singh Majithia.

Sada Kaur died in confinement in December 1832.