Rukmini was the daughter of Bheeshmak, the King of Vidarbha. She is believed to be an incarnation of Lakshmi and is worshipped for being the goddess of fortune.
As mentioned in the Mahabharata and the Puranas, if there is any other woman as beautiful as Draupadi, it is Rukmini. She is known as the Swarup-shakti and Jagatkari, the Mother of the Divine world.
When Rukmini's elder brother, Rukmi, wanted her to marry Shishupal, the crown prince of Chedi, Rukmini refused. Since childhood Rukmini had heard stories of Krishna and wanted to marry him. She wrote a letter to Krishna in which she expressed her love for him and told him that she would only marry him and nobody else.
Rukmini was abducted by Krishna on the day she was supposed to marry Shishupal. It was well known that Krishna loved Rukmini more than his other wives.
To prove this Narada asked Krishna's wives to give Krishna away in charity and claim him back by offering wealth which is of the same weight as Krishna. Krishna's wife, Satyabhama, lost Krishna to Narada by giving away all her jewellery. The weight of her jewellery could not match Krishna's weight on the weighing scale.
When Narada told them that he would sell Krishna to the cowherds, Rukmini, with a prayer to Krishna, placed a Tulsi leaf on the scale. That single leaf outweighed Krishna. Since that day, Rukmini came to be known as Tulabhrami.