All indications are that, following the death of her husband, Hugh WANTON, Christian reverted to her maiden name for the rest of her life.

Additional details revealed by the Arngask parish register in connection with Christian’s death: [6207]
(1) Christian was classified as “a pauper.”
(2) A John FERGUSON was paid for digging the grave (same day as burial).
(3) 12 May 1844: a James SIMPSON was paid for the coffin, the shroud and other funeral expenses. Note that the 1841 census shows that a James SIMPSON, age 25-29, lived in the same neigborhood as Christian, and his occupation was “Wright” which means craftsman. [6208]
(4) 16 May 1844: the parish paid a half-year’s rent which was due on the home where Christian had resided.

There was a Christian Ferguson WINTON who died in 1828 in Edinburgh, and was buried at Saint Cuthbert's Churchyard. But that woman was the wife of George WINTON (1759-1822). That puts him in the generation where he could potentially be a brother or first cousin of Hugh Winton/Wanton, but it appears that George was born in Edinburgh. On the other hand, it is still unknown where Hugh was born.

09-FEB-2018: the following search on ScotlandsPeople found one “Christian FERGUSSON” (2 other hits had the surname “FERGUS”) born 13-MAY-1770, in the parish of Ferry-Port-on-Craig, Fife (present day Tayport). Father was John FERGUSSON, mother was Margaret FERGUSSON.
You searched for: Event: '(B OR C OR S)', Church_type: 'Old Parish Registers', Surname: 'Fergus', Surname Option: 'Starts', Forename: 'Chris', Forename Option: 'Starts', From_year: '1760', To_year: '1770', County: 'FIFE'
Birth in 1770 seems a bit late and certainly doesn’t fit with age reported in 1841 census. But either or both could be innacurate dates.

Modifying that search to look at Perth instead of Fife, produced 23 hits: 14 spelled FERGUSON, 9 spelled FERGUSSON. Most were “Christian” but one was “Christiane.” 12 parishes were represented, but not Arngask. 2 were for the year 1767, one in Balquhidder, one in Fortingall.