You need to supply more info. Unable to find marriage in Birkerød parish on the given date.
If Benthe was 67 when she died in 1817 she was born in 1750 and would have been 37 in the 1787 census, but I have not found anyone where age parish and census fit together, searching on Benthe alone. A girl kept her maiden name throughout her entire life at that time, so a different surname is a different person. To find out more I need the names of her children, when they were born, whom they married etc.
Regards, Hedvig Pitzner-Jørgensen