Sophia was a daughter of Theodore II Palaiologos, Marquess of Montferrat, and his second wife, Joanna of Bar.
[1] Manuel had sent Nicholas Eudaimonoioannes as ambassador to the Council of Constance while seeking Papal permission for the marriage, as the issue was the conversion of the Roman Catholic bride to the Eastern Orthodox Church.
The permission was granted by Pope Martin V. Apparently although Sophia was a particularly pious individual, unfortunately for her marriage, she was also considered unattractive by the standards of her time, described by Doukas as "Lent in front and Easter behind".
[2][3] John VIII, not content in his marriage, made every effort to avoid her, and as a result, Sophia spent much of her time in Constantinople isolated from her husband.
However, Sphrantzes records that in August 1426 Sophia "fled the City [Constantinople] and returned to her homeland", and that a little more than a year later John VIII made Maria of Trebizond his wife.