The first Most Holy and founder of the Church — born at Karven, which is famous for it and is a major pilgrimage site because of it. (S7)
The Augustinian Calendar (year 1 = founding of the Church, 275 MCY) is presumably named for her — see Timeline. (Presumed from the name; nobody has stated it.)
Speculation
The founder of the whole Church was born in what is now Hazad — and her birthplace-city belongs to House Balventia, the church dynasty Uncle has cultivated for years. The Eastern Church’s claim to be the older, purer rite is not just rhetoric; it has geography.