The 1875 Norwegian census databases are NOT complete. There are entire sections of Norway not included in those databases.
Any events for her which might have been recorded in the parish records would be found as part of Sem, Vestfold (after 1739). Norway did not do "household surveys" but recorded births/baptisms, confirmations, marriages, deaths/burials, and perhaps persons joining and/or leaving the parish.
The Digitalarkivet web site - (http://digitalarkivet.uib.no/cgi-win/WebFront.exe?slag=vis&a...
An English option is available by clicking on that word from either the left hand column or the blue link bar along the bottom of the homepage.
The scanned images are available from the homepage link "Skanna kyrkjebøker" [Norwegian version]/"Digitised parish records" [English version] which is listed along the left hand column and from the blue banner of links along the top section of the homepage.
When you click on that link another page will present a short list of choices - choose "Read the digitized parish registers"[English version]/"Lesa skanna kykrebøker" [Norwegian version].
After you've clicked on that link and a new main page has presented on the screen be sure and read the instructions that are available from the Digitalarkivet for navigating the scanned records. The instructions are available in Bokmål (official Norwegian), Nyorsk (Norwegian), Davvisámegiella (Saami), and English.
Recommended basic reading are the "Startsiden" [Norwegian version]/"Main page" [English version], "Brukerveiledning" [Norwegian version]/"User's guide" [English version] and "Om tjenesten" [Norwegian version]/"About this service" [English version].
Good information about translating the formats of Norwegian parish church records during various time periods, many of the basic terms used and understanding how to use the information should be studied at this web site -
Norway has a tradition of publishing history and genealogy books for many rural districts of the country called 'bygdebøker'. For Slager you could look for "Sem og Slagen, en bygdebok", authors Oscar Albert Johnsen; Thordis Johnsen, E. W. Orholt, and Sigurd H. Unneberg.
Learn about 'bygdebøker' (http://homepages.rootsweb.ancestry.com/~norway/bygdebok.html
Bygdebøker and Ættarbøker can be helpful but are definitely secondary sources of information -- any research done in them should be verified in the primary sources such as the parish church records.