Douglas,
The 1841, 1881, 1891 and 1901 PEI censuses can be searched online at:
http://www.edu.pe.ca/paro/census/build.asp and the 1911 census at:
http://automatedgenealogy.com/census11The Susan DOUGAN I found in the 1881 census appears to be living with Anthony, aged 27, and Katie, aged 0 (I assume husband and newborn child).
In the 1891 census they are a big family listed as DUGGAN:
ANTHONY DUGGAN aged 38
SUSAN 36
KATIE (KATY) 10
MAY 8
GERTY 8 (Gertrude in the 1901 census)
ELLA 6
EMMA 5
IRENE 3
MAGGIE 2 (M. Ethel in the 1901 census)
MARY JOSEPHINE (JOSEPH) 0
WILLIAM (WM.) 67
I would guess that William is Anthony's father.
The family appears again in the 1901 census. I have not checked the 1911 census.
I hope this is your Susan.
Jim