[1] Her father was executed for his part in the Rising of the North and her mother who had been involved, left the country with the infant Mary.
Her siblings were left in England and brought up by their paternal uncle, Henry Percy, 8th Earl of Northumberland.
She purchased a house in Brussels and asked Benedictine nun Joanne Berkeley to be abbess.
[1] Difficulties arose between those nuns who wanted a Jesuit confessor and those who preferred a different spiritual approach.
[6] Berkeley died in 1616 and Percy was elected abbess, serving until her death in Brussels on 13 September 1642.