Neela wasn't convinced of the importance of Rukmini. She says, that Radha Rani was the prime consort of Krishna and Rukmini does not have the importance that she deserves. So to pacify her, this post.
The Principal Queen and closest wife of Krishna, Rukmini, was the Daughter of King Bhismaka of Kundil, Upper Assam. Bhismaka was a political ally of the King Jarasandha of Magadha. He had two children. Rukmi (the son) and Rukmini (the daughter). Rukmi wanted Rukmini to marry Shishupala, another ally of Jarasandha. Rukmi was against the marriage of Krishna and Rukmini because Krishna had slayed the Evil King Kamsa who was a friend of Rukmi.
Rukmini was in love with Krishna for his qualities, courage and divine presence. And Krishna also fell in love with Rukmini, for she was considered the most virtuous women of all times.
Balarama battled with Jarasandha while Krishna duelled with Rukmi. Krishna was inevitably victorious and so brought Rukmini to Dwarka and married her with great pomp and ceremony.
Rukmini is a representation of silent devotion. Her devotion to Krishna is expressed in the Tulabharam incident. Satyabhama in her pride once takes a vrata when she has to give away Krishna to Narada and then buy him back by giving away gold and jewellery of the weight of Krishna. After mobilizing all the money that she can when she is not able to do so, Narada advices her to gulp her ego and ask for help from Rukmini.
Rukmini removes all the wealth from the weighing scale and just puts one leaf of Tulsi with all her devotion. The leaf weighs much more than lord Krishna. This signifies how a single leaf of devotion can weigh more than the Krishna himself, who carries on his shoulders the weight of all the three lokas.
Rukmini was Lakshmi Incarnate. As Vishnu is Vishnu's Shakti, Rukmini is Krishna's strength and driving force. Though Krishna is matter, or existence itself, it means nothing without the moving force (Rukmini) that puts everything into action.