Shri Sita Thakurani is to be worshiped just as much as Sachi Devi herself, as the mother of the universe. She is the eternal wife of Shri Advaita Acharya. She was the daughter of Shri Nrishinga Baduri. She was married to Shri Advaita Acharya in Phuliya Nagara. After their wedding, Advaita Acharya went to Nadiya, to live in Shantipura. Sita Thakurani was always absorbed in vatsalya prema for Shri Gaurasundara Prabhu, and, out of parental concern used to instruct Jagannatha Mishra on how to care for the boy.
Shri Krishna Dasa Kaviraja Goswami has described the birth celebration at the house of Jagannatha Mishra upon the advent of the Lord, giving special attention to the position of Shri Sita Thakurani. Advaita Acharya's wife, worshipable by all the three worlds was Sita Thakurani. Taking the Acharya's orders on her head, she had come to take a look at this new child, this jewel of jewels, and to offer Him presents.
On the eve of his son's advent Shri Jagannatha Mishra, seeing the imminent signs of his child's arrival, sent word to Advaita Acharya in Shantipura that the long-awaited child was being born. Hearing news of the advent of this unprecedented child, Advaita Acharya floated in the waves of ecstasy. With Shri Haridasa Thakura, he went to bathe in the river, and, after much dancing and song, he sent his wife to go quickly to Mayapura in Navadwipa.
According to Gaura-Ganodesha-Dipika, Shri Sita Thakurani is Yogamaya. The Gaura-Parshada-Charitvali says that in Krishna Lila, she was Purnamasi, the mother of Sandipani Muni, grandmother of Madhumangal and Nandimukhi and a disciple of Narada Muni. (Gaura-Ganodesha-Dipika, however, says that Paurnamasi in Krishna-lila became Shri Govinda Acharya in Chaitanya lila.)
In Dvapara-yuga, during the celebration of Krishna's birth ceremony, she was present in the house of Nanda, and at that time gave Nanda and Yashoda many instructions on how to care for the child. The Chaitanya-Charitamrita gives the following account of Sita Thakurani's visit to the house of Jagannatha Mishra after the birth of the Lord:
"One day, shortly after Shri Chaitanya Mahaprabhu was born, Advaita Acharya's wife, Sita Devi, who is worshipable by the whole world, taking permission of her husband, went to see that topmost child with all kinds of gifts and presents. She brought different kinds of golden ornaments, including bangles for the hand, armlets, neclaces, and anklets. There were also tiger nails set in gold, waist decorations of silk and lace, ornaments for the hands and legs, nicely printed silken saris and a child's garment, also made of silk. Many other riches, including gold and silver coins, were also presented for the child.
Riding in a palanquin covered with cloth and accompanied by maidservants, Sita Thakurani came to the house of Jagannatha Mishra, bringing with her many auspicious articles such as fresh grass, paddy, gorochana, turmeric, kunkuma, and sandalwood. All these presentations filled a big basket. When Sita Thakurani came to the house of Sachi Devi, bringing with her many kinds of eatables, dresses, and other gifts, she was astonished to see the newly born child, for she appreciated that except for a difference in color, the child was directly Krishna of Gokula Himself.
Seeing the transcendental bodily effulgence of the child, each of His nicely constructed limbs full of auspicious signs and resembling a form of gold, Sita Thakurani was very much pleased, and because of her maternal affection, she felt as if her heart were melting. She blessed the newly born child by placing fresh grass and paddy on His head and saying, "May You be blessed with a long duration of life." But being afraid of ghosts and witches, she gave the child the name Nimai. On the day that the mother and son took bath and left the maternity room, Sita Thakurani gave them all kinds of ornaments and garments, and then also honored Jagannatha Mishra. Then Sita Thakurani, being honored by mother Sachi Devi and Jagannatha Mishra, was greatly happy within her mind, and thus she returned home."
From that day on, Sita Thakurani would often come to Mayapura from Shantipura, in order to teach Sachi mata how to care for the new baby. She would give her many different instructions on how to raise children. And after helping with the child in this way, she would return to Shantipura. When it came time for the child's birthday ceremony, Jagannatha Mishra and Sachi Devi let the worshipable Sita Thakurani be the first to offer the child his new clothes.
Advaita Acharya Prabhu also had a house in Navadwipa. There he would live from time to time and discuss Krishna-katha with the Devotees headed by Shrivasa, diving and surfacing in the waves of joy until the break of dawn. After Shri Gaurasundara's appearance, all the Devotees prayed together with Shri Advaita Acharya and Sita Thakurani that the child might live long in Mayapura and have good fortune.
Sita Thakurani and Sachi Devi were of one mind; the baby Nimai was their life and soul. Every day Sita Thakurani would go to the house of Sachi Devi and help her with the care and nurturing of the boy. In the house of Jagannatha Mishra, the divine child increased the pleasure of the eyes and minds of all the Devotees, just as the waxing moon gradually grows more brilliant with each passing day.
After several years, when Jagannatha Mishra's son Vishvarupa – Nimai's older brother – had grown up, he suddenly took sannyasa. The grief and agony of Jagannatha Mishra and Sachi Devi upon their son's leaving was great. Gaurasundara was also dismayed and unhappy at his brother's separation. At that time Advaita Acharya and Sita Thakurani consoled Jagannatha Mishra and Sachi Devi, and helped take care of Nimai.
Shrivasa Pandit's wife Malini Devi also was always very affectionate towards the child, nurturing Him and caring for Him. She and Sachi Devi were of one mind in doing this.
After exhibiting His childhood pastimes, Nimai gradually progressed into His Kishora-lila, or pastimes of youth. After some time, He went to Gaya and revealed His true form and real purpose. Having returned from Gaya He gathered all the Devotees at the house of Shrivasa Angan for the purpose of beginning kirtan. At that time, Advaita Acharya brought Sita Thakurani from Shantipura to Mayapura, and, having arrived there was the first to worship the lotus feet of Shri Chaitanya.
Gradually Shri Gaurasundara began, in Navadwipa, to unfold His kirtan pastimes, wishing to deliver the fallen souls. As time went by He took sannyasa and turned His face towards Vrindavana, and ran off, half mad into the jungle in search for Shri Krishna. Upon hearing this, Shri Sita Thakurani spent four days with Sachi Devi, who, plunged in the darkness of separation as if the sun had left the sky forever, lay fallen on the ground like one near death.
Shri Chaitanya Mahaprabhu, being bound by the ropes of love, was unable to go to Vrindavana, but was drawn to return to Shantipura. When He arrived in Shantipura, Advaita Acharya and Sita Thakurani felt as if their life has returned. After having fasted for four days, Shri Gaurasundara accepted Prasada cooked by the hand of Sita Thakurani.
Previous to taking sannyasa also, Shri Chaitanya Mahaprabhu along with Nityananda Prabhu would, from time to time go to the house of Advaita in Shantipura, where they would have a festival and perform Krishna-nama-lila-kirtan all day and all night. The beautiful nature of this subject has been described by Shri Parameshvari Dasa Thakura in his Shri Pada Kalpataru as follows:
One day the Lord laughed, having arrived in the Temple of Shri Advaita and thus the son of Sachi took His seat. Along with Nityananda, Advaita sat down, and the two of them began playfully assessing the idea of having a festival. Hearing all this, Sita Thakurani entered smiling. At that time, in sweet words which made the minds of those who heard them blissful, the son of Sachi ruled that there must be a great festival. He said, "Listen Sita Thakurani: we shall extend invitations to all the different Vaishnavas who live nearby. Let whoever hears the sound of our song, resounding through the air, come and join us. We shall invite one and all."
Saying this, Shri Gaurachandra gave orders to the Devotees saying,
"You, invite the Vaishnavas."
"You, ready the mridanga and karatalas."
"You, prepare sandalwood and aguru for distribution."
"Have everything ready at the ghat."
"Carrying out these assignments expertly, and after garlanding the Devotees with flower garlands, the Devotees shall gather together in a circle for an uproarious kirtan."
Hearing the words of Mahaprabhu, the Devotees followed His orders with great affection, collecting garlands, sandalwood, betel, ghee, honey, and milk, and everything else essential for worhsiping the Lord. The different gifts and fragrant articles for the Devotees and the Lord were then distributed in the proper ways. The kirtan began at midday. At that time everyone chanted "Hari! Hari!" and the mridanga made the whole kirtan auspicious. Thus swims Parameshavara Dasa in the rasik pastimes of the Lord.
After Shri Chaitanya Mahaprabhu took sannyasa and went to live in Jagannatha Puri, Shri Advaita Acharya and Sita Thakurani used to go and visit Him each year, bringing their son Achyutananda with them. On one such occasion, Sita Thakurani prepared some of the Lord's favorite preparations for Him and invited Him to their home to take lunch. Simply to increase their ecstasy, the Lord, who was always absorbed in Krishna Nama, honored their invitation and took lunch in the home of Advaita and Sita.
When Sachi and the people of Navadwip heard that Gaurahari was at Advaita’s they all came there to visit Him. Seeing Him in His dress as a sannyasi, they were felt joy mixed with separation. Sita Thakurani prepared an immense meal and served it on whole leaves from seed-banana trees. As Mahaprabhu and Nityananda ate, Advaita Prabhu talked and joked with them. This has been extensively described in the Chaitanya Charitamrita’s Madhya-lila, chapter 3. Mahaprabhu afterwards also ate foodstuffs prepared by Sachi Devi in order to ease the suffering He had imposed on her by His departure. The reunion of Devotees turned into a great festival, and Advaita’s house in the town of Shantipur was transformed into the city of Vaikuntha.
Sita Thakurani, being always overwhelmed with vatsalya-prema treated Him as affectionately as if He were her own son. The Lord Himself also treated her with the same kind of regard and affection that He had for Sachi Devi herself. Shri Sita Thakurani bore three sons, Achyutananda, Krishna Mishra and Gopala Mishra, who were followers of Shri Chaitanya Mahaprabhu.
According to Bhakti-Ratnakara, Shri Sita Thakurani's father was Shri Nrishimha Baduri. Sita Thakurani also had a sister, Shri. According to the Gaura-Ganoddesha-Dipika, Sita Thakurani, the wife of Shri Advaita Acharya, is Yogamaya, and her sister Shri is the prakasha, or manifestation, of Yogamaya. (yogamaya bhagavati, grihini tasya sampratam, sita rupenavatirna, "Shri" namni tat prakashatah)
[Excerpted from the Vrinda website and “Shri Chaitanya: His Life & Associates” by Shrila Bhakti Ballabh Tirtha Maharaja]