In the 1860 census, Philena McIntosh (age 22, born NH) lived in Berlin VT with Mary Seaver (age 50, probably the wife of Elijah Seaver).
You have the 1870 census data, showing Clara McIntosh living with Elijah and Mary Seaver in Berlin VT.
In 1880, Elijah Seaver (age 74) is in Fayston VT, with daughter Clara J. Barrett (age 19), son-in-law Cassine Barrett and grandson Walter L. Barrett.
The circumstantial evidence is pretty shaky.You could deduce that Clara was the daughter of Philena (Seaver) McIntosh, and that Elijah/Mary adopted her, but there are a lot of "what ifs" in that deduction.A formal adoption in the 1870's might be found, and would pretty much prove the case.
Have you looked for Philena in the 1880 census?
I have ancestry of Elijah Seaver if you want it in a genealogy report.