I don't have any evidence for you but I will bet my house and souls of my children that the death date of Bibianne Blanchard is incorrect.
1835 is the year of their marriage and what will quite commonly happen in genealogy is that a technically accurate genealogist will list that the last date supported by a source for Bibianne is the marriage record inn 1835. A less rigourous family tree enthusiast will create a profile for Bibianne based on the technically accurate tree but assuming the last known date is the date of death.