Hi Mark,
According to the 1802 marriage recorded in Oborne, Susannah ALLEN was "of this Parish" whilst Titus was "of Buckland Newton" - so perhaps you'd need to know more about her natal family to understand why she would be of Oborne.
According to Militia lists for 1798/1799, Titus FOOT (and a number of other FOOT men) lived within the tything of Plush, which is in the Union of Cerne.
Did Titus die in 1838, at the Union Workhouse of Cerne. Buried Cerne Abbas ?
If he did - then sadly, I don't think the 1861 Susannah FOOT is yours (unless she remarried another FOOT)?
1851: Sharnell, Buckland Newton, Dorset
HO107- Piece 185/ Folio 81 /Pg29
Head: Thomas FOOT 73, Pauper, b Dewlish, Dorest
Wife: Susannah FOOT 70, Pauper, b Buckland, Dorset
Lodger: James WARR 36, Marr, Labourer, b Palham, Dorset
Lodger: Jane WARR 35, Buttoner, b Buckland
1861: Sharnell Green, Buckland Newton, Dorset
Head: Susannah FOOT 80, widow, b Mappowder
Lodger: David WAR 34, mar, Ag Lab, b Glanville Wooten
Lodger: Jane WAR, 47, mar b Buckland
Nep-hew: David WAR 32, unm, Ag Lab, b Glanville Wooten
Cheers
AMBLY