> "Some family members are found interred at Little Cedar Cemetery, Adams, Mower County. However, I do not see a reasonable match for Siri (Sarah)." <
What family members are buried there? Her parents? Sarah may have died before the 1880 census. Since she died shortly after her parents, it seems likely she was buried near them.
Where don't you see Siri/Sarah? Cemetery records? Find a Grave? Interment.com?
Where are her siblings in 1880?
1875 Minnesota Census at Minnesota Historical Society, here is a Sarah Anderson age 10 in Marshall, Mower, Minnesota:http://people.mnhs.org/census/Results.cfm
Were the children born in Norway? Was Siri?
No particular reason to think the girl below is "your" Sarah - just a "possible" for the shoebox.
Sheldon, Houston, Minnesota
Mary Lynch 55
Catharine Lynch 20
Edward Lynch 14
Andrew Olson 20
Sarah Anderson 15 laborer