Seeking information on Ragnilda Barsnes

Ragnilda Barsnes is my 2nd great grandmother. I am looking for any information on her parents, family in Norway and her immigration to the US. Any information would greatly appreciated. We have limited information on her. She was born in Norway in abt 1853. She died in 1883 near Garretson SD. She was the first wife of Nils Olson Viken who later took the name Boyum. Nils arrived in America in 1870 on the ship the Mercator. He appears to be alone and unmarried. He married Ragnilda Barsness in approx 1873 we believe in Wisconsin. I can not find any records of this or her on the census records. I have seen emails that they were married in Spring Grove WIS. Nils and Ragnilda left for the Dakota terr. and homesteaded in Dakota Terr. North of Sioux Falls. There is a Knute and Berta Barsness in Minnehaha county during 1880-1900 but I can't connect them to her. Nils belonged to the St Paul'is congregation but in the church records I can't find that Ragnilda was buried there. His 2nd and 3rd wives are buried there. Thank you, Paul Jankowski