According to tradition, Nina (or Christiana) was a slave and related to George. She was taken prisoner of war by Emperor Constantine. In prison, she is said to have led many people to the Christian faith through her prayer and her exemplary life; according to other tradition, she fled and reached the then Kingdom of Iberia on foot, where she settled in its capital Mtskheta. She was powerful in medicine, the news of which came to the ear of the sick wife of King Mirian III, Nana, who secretly called her and after Christina had healed her also converted to Christianity. When King Mirian was also miraculously converted in 322, he declared Christianity the state religion in 337 and asked Emperor Constantine to send missionaries, who then came from Constantinople – today’s Istanbul.
Joachim Schäfer: Article Christiana of Georgia, from the Ecumenical Dictionary of Saints – https://www.heiligenlexikon.de//BiographienC/Christiana_von_Georgien.html