Is there a Saint Fiona

Answer 1

No

The Catholic Church recognizes a St. Fionnchu - Abbot of Bango Abbey Abbey, in Ireland, the successor of St. Comgall who lived in the 6th century. His Feast day is 28 November.

The Catholic Chruch also recognizes a St. Fina - a young girl whose claim to be recognized as a saint lay in the perfect resignation with which she accepted bodily suffering. According to her official biography:

Her head, hands, eyes, feet and internal organs were affected by some disease and paralysis supervened. Although in terrible pain she always maintained serenity and with her eyes fixed upon the crucifix she kept on repeating,"It is not my wounds but thine, O Christ, that hurt me". Eventually her mother, who cared for her when she was not out working (her father had died some time prior) died and she was left destitute with no one to care for her and no one wanting to since she was rather repugnant from all the sores. She used to pray that she might have patience in her affliction.

That's as close as you get to a "St. Fiona".

Answer 2

I can find no reference to a saint named Fiona.