If you haven't already try La Salle County Genealogy Guild - lscgg dot org. Their searchable database of death certificates lists neither of these women, but their obituary file contains a published obituary for a Mrs. Berge 3 Apr 1903, and also a Christina (Mrs. George) Berge from 29 Sep 1916. An Esther Carlson married Merle Henry Hougas 28 Nov 1917 in La Salle Co. A quick search on familysearch found a George and Clara (Muhlstadt) Berge (birth years similar to those on the stones) married in 1920 in Rock Island county and there on the 1930 and 1940 censuses. George died in Rock Island county, so if this is that couple she could have died in Iowa as they were on the border just over the river, or sometime after 1950 as that is as late as the IL indexes go. She could also have been remarried and/or buried elsewhere at a later date.