As described at Locating an elusive UK birth record (Mary Ann Harper born circa 1865 possibly Dudley, England)? Mary Ann Harper is particularly elusive.
Two years before her marriage at age 18 I'd expect to find her in the census with her parents (father James Harper, unless she lied and was illegitimate) or in service locally (either Dudley where she was supposedly born or close to the parish she married in in 1883) but I haven't tracked her down.
What techniques can I deploy to locate her in the 1881 census?
What I do know:
Mary Ann Harper (spinster, aged 18) was married after Banns on 15th April 1883 to John Stanley Wright at St. Lukes Church, Birmingham, Warwickshire, England. She named her father as James Harper (deceased) with no occupation given. Both parties gave their address as Hill Street. The witnesses were a J. Marshall and a D. Marshall. [Source: Copy of the relevant entry of marriage from the General Register Office]
From census records after her marriage, I have: an approximate year of birth (1865), and supposed place of birth (Dudley, England).