The history of shriRani Sati dadi maa starts from the time of Mahabharata. It is believed that dadi Rani Sati is incarnation of Devi Shakti. During MahaBharata war, Abhimanyu was martyred in the battle. Uttara was Abhimanyu's wife. She prayed to Krishna that she wants to go Sati with her husband. However she was pregant and Krishna granted her wish of being married to Abhimanyu and her desire to be sati in her next life.
As granted by Lord Krishna, in her next life she was born as the daughter of Gursamal in the village of Dokwa in Rajasthan. She was named - Narayani. Abhimanyu took birth in Hissar as son of Jaliram and named - Tandhan. Tandan and Narayani got married and were leading a peaceful life. He was in possession of a beautiful horse which was being eyed by the son of king of Hissar from quite some time. Tandan refused to hand over his precious horse to the king’s son.
The king’s son then decides to forcefully acquire the horse and thus challenges Tandan for a combat. However Tandan fights the battle bravely and kills the King’s son instead. The enraged king thus kills Tandan in front of Narayani in the battle. Narayani symbolic to female bravery and power fights with the king and kills him. She then commanded Ranaji (the caretaker of the horse) to make immediate arrangements for her to be set ablaze along with her husband’s cremation.
Ranaji playing a vital role in fulfilling her wish to be sati with her husband is then blessed by Narayani that his name will be taken and worshiped along with her name and since then she is known as Rani Sati.