Laura,
Here is what I know. Johann Julius Splettstoesser (Splettsloesser) was born 1842 in Gollin, West Preussen. He married Henrietta Henke, who was born 1840 in Prellwitz (Przelewice), West Preussen. Using today's description,this area is in Eastern Germany and western Poland. Gollin and Prellwitz are about 7 miles apart. Their marriage date was March 29, 1867 in Prellwitz. This information from the LDS familysearch.org website. Their children were Maria Augusta Splettsloesser, born Feb 4, 1868 in Gollin, your ancestor Bertha Emilia Splettsloesser, born May 10, 1869 in Gollin, and another female born March 9, 1871 in Gollin who died the following day. I do not know what happened to the first child, Maria, but she is not listed in the 1880 census.
Based on the birth of these children, I believe they immigrated sometime between March of 1871 and May of 1872. The next daughter is Emma Antoine Henriette Splettstoesser, born May 11, 1872 in Berlin Wisconsin. A son John was born in August of 1875.
Henriette Henke Splettstoesser died giving birth on May 8, 1881 and is buried on Sam Redetzky's farm in Berlin township, Marathon county. She was 40 years old.
Her husband Johan Julius (we know him as Julius)Splettstoeser briefly married and divorced, and then married a widow named Wilhelmina Ladwig on April 18,1884 and they had a son Herman Splettstoeser on April 19, 1885. This is my line.
As you know, Bertha married Pierce Eschenbauch,had 10 children, and died in 1913 at the age of 44. She is buried in Pine Grove Cemetery in Wausau.
The second surviving daughter Emma Antoine Henriette (called Henriette) married John Egeler, had 4 children and died in 1930 at the age of 61. She is buried in Restlawn Memorial Cemetery in Texas township.
Their son John Splettstoeser married Madelan Vonderheiden and died in 1949 at the age of 73. They had one daughter named Henrietta and lived in Eau Claire.
Youngest, Herman Splettstoeser married Mathilda Pattinger and had 3 sons. He is buried in Pine Grove cemetery.
Funny story...when my oldest son was in 7th grade he started a new school. (We live in a suburb of Minneapolis) He did not know anyone in his classroom, but made close friends with a young man. I went on a field trip with the class and learned from this kid's mother that their family originally came from Wausau. We discovered that they were descendants from Bertha Splettstoeser Eschenbauch, and my son was descended from Herman Splettstoeser. They were related! Funny how they landed together and became friends over a hundred years and 200 miles later. They loved telling everyone that they were cousins!