In case this is a match to your Bertha Stark in Milwaukee, there were death notices in the local German papers for a Bertha Stark (63 yrs.; husb. Andrew Stark) in Sept. 1925.
Indexing Milwaukee's German newspapers continuously since 2007 ...
Gary Rebholz, compiler/editor
"Milwaukee's German Newspapers; an index of death notices and related items" (1844-1950).