Note that the Hannah Gaskill, dau. of George and Data Gaskill, aged 35, has a marriage record in Milford, MA in 1847 and not as a widow and listed under her Gaskill maiden name, as she married a widower Samuel Chase.
Therefore, I would disregard the previous as the above gives dispute to parentage of the Hannah Gaskill who married in 1827, unless her Gaskill name in 1847 was incorrect and it was her second marriage (but not by death of Caleb Thayer unless elsewhere than in Mendon).
Thus the marriage in Mendon must be a different Hannah Gaskill but no connection of another Hannah Gaskill found yet to match the time frame of a marriage to Caleb Thayer. The Mendon records haveThayer children from the marriage.
I hope someone has more on these Gaskill to identify if there was another Hannah, maybe born before 1811.