Drusilla Bigford Cutler was born November 15th, 1820 in Shefford, so she could not have been Anthony Cutler Jr., and Bethany Allard's daughter as they gave birth to a daughter named Precilla Cutler in March 1821.
Bethany's sister Mary married David Kineson October 24th, 1823 in Shefford so if Drusilla was adopted by Mary and David, she must have been at least 3 years old at the time.
Anthony's brother, Roswell Cutler married September 10th, 1821 in Shefford to Lydia Wood, daughter of Hezekiah Wood and Lydia Savage. Their first child was born July 21st, 1822 in Shefford so Drusilla may have been Roswell's daughter but I doubt it as Lydia would have been 7 month pregnant at their wedding.
Anthony's brother Prosper Cutler married in Dunham September 18th, 1828 to Aurilla Gleason. I doubt strongly they were Drusilla's parents, although Prosper may had a daughter prior to his marriage to Aurilla Gleason as Prosper was 22 years old when Drusilla was born. Sadly I am not able to connect Drusilla to Prosper Cutler.
Anthony's brother calvin married November 18th, 1821 in Dunham to Susan Ware. Calvin could be Drusilla's father but doubt it very much... so that leaves you with the only strong clue which is Prosper Cutler.
Anyway Drusilla married at the Methodist Church in Shefford to Frederick Halloway Kenny, a farmer from Stukely. They had six children: Marcus M., Nathan, Levi R., Mary Elizabeth, Myron Sanborn, and Corilla Wood. After the birth of their daughter Mary Elizabeth in 1847, they moved to Danville, Vermont. At about 1855 they moved to Wayne, Iowa. By 1863 were living at Scothch Grove, Iowa where Frederick was drafted in the Civil War. In 1870 there were living at Milo, Iowa, a few years later in State Center, Iowa where they both died and buried at the Hillside Cemetery. Drusilla, November 13th, 1880 and Frederick, August 17th, 1896.
Hope this helps!!