Do you have Louis' obit? Just in case, I'll attach it.
It looks like Sophia is still alive for the 1905 census in Racine. Is she also Henrietta that appears in the 1910 census with Hans and Agnes along with Carl and his family or did Hans re-marry? Hans and Henrietta are also the same age in the 1910, married once each for 39 years and she is the mother of 6 and both immigrated in 1869 which would be off by 2-3 years according to Louis' obit.
I haven't located their deaths or burials but it looks like your Sophia Mary now has another name, Henrietta.
Do you connect to one of their children? It looks like Agnes remained single and became a nurse in Chicago.