How do I find a Norwegian of Swedish ancestry?

For almost 5 years I have thought I had one line from Norway pretty well whipped. I had passenger info from both the Norway side and the Ellis Island arrival. I had parish records for several generations and some census data from Norway, 1910-1920 US censuses, US birth and death records, etc. Two days ago I found the person (Louise Larson born Telemark ca 1887) still living in Kragero in 1910... 3 years after mine had married in Chicago! In spite of several rationalizations, the last two days have made me think that I have the wrong ancestry for her, but there is nothing I can find in any records that prove it either way. Death records put her birth date as Mar 1887, and the person in the 1910 census was pretty definitely born in Dec 1887. So my main QUESTION IS: Is there any way to track down the birth/christening of a person who's father was Swedish who probably was not a member of the Norwegian church? I have checked for baptismal records for Louise and her sibs as listed on the 1900 census. Here's the link: http://digitalarkivet.uib.no/cgi-win/WebCens.exe?slag=visbase&sidenr=6&filnamn=f00816&gardpostnr=384#nedre If that doesn't work, head of house is Emil Lars. born 1852. Louise appears to leave Norway 12/15/1904 for Chicago (under name Aase Louise Larsen, age 16), and arrives Ellis Island 12/26/1904 as Louise Larsen. Any help gratefully received. Nick