It said in the book (page 231) that the children had disagreements about where she should be buried, with some wanting her buried with her father and sisters in North Dakota, but she was buried in the frozen ground of the cemetery of the Wilmington Lutheran Church that they had attended. (New Wilmington Cemetery vs Old Wilmington Cemetery). The book said that her marker reads "Martini Twite". The Wilmington Cemetery records match her dates (1871-1960).
Are you in the La Crosse area?