I have found the Census data at familysearch but it doesn't list an occupation. Is an occupation listed for Mary? Her husband, William G. Allen, is listed as Professor Of Music.
Name: Mary E Allen
Event Type: Census
Event Date: 1871
Event Place: Islington, London, Middlesex, England
Enumeration District: 27
Gender: Female
Age: 39
Marital Status: Married
Relationship to Head of Household: Wife
Birth Year (Estimated): 1832
Birthplace: Malone, United States
Thanks,
Bob