I checked the cemetery records for Washburn Co., but could not find anything for Rebecca A Robinson. There are several William Robinson's buried in the Viola Lake Cemetery located in Burnett Co., but they are not who you are seeking...
one being a William L Robinson, b. 1878 - d. 1935 and the other being a William Charles Robinson, b. 1956 - d. 02 Feb 1957 (11 mo, 15 days old)

Sorry I couldn't be of more help to you.