I suppose Elinor Christian als Christian might still have had sisters alive in 1822 when she was 91, or when she dictated her will in 1811.
There was an Ellin daur of William Christian & Isabel [Kerrish?] bapt Maughold 22 Jan 1730/31 (sisters Jane & Elizabeth).
And an Ellen daur of John Christian & Cath bapt 29 July 1731 (sister Hannah).

The Radcliffes wrote that the Ellinor Christian who married William Christian of Ballaterson was from Ballure, which means that her father was John Christian whose first wife was Catherine Cowle who died in 1740 (will Maughold E 1740-2?) and made her two daughters Ellinor (b.1731) & Hannah (b.1734) her execs, asking her husband to give them a considerable sum of money. Her burial was followed in the register by "Tho Christian her only son (under age)".
William Christian married again, to Dorothy Callow of the Claughbane family - perhaps where the name "Dorothy" came from in the later generations, rather than from Dorothy Wattleworth? - she might have been a nice step-mother! (Her decree Maughold E 1745-3?). Dorothy had only sons bapt. Maughold: John & Robert - John being Capt John Christian 1742-1823. So Elinor had no sisters bapt Maughold other than Hannah.
Sisters could be in-laws, or her daughter sisters Elinor & Isabella. Not that it helps us with her daur Elinor's husband William Corkill, if she was the Elinor he married.

Re. the Elinor Christian als Wattleworth you noticed who was bur 11 Nov 1826, she could have been from the Maughold family of John Wattleworth & Ellinor Christian, bapt 30 Dec 1785. Wattleworth wasn't a common name in Maughold. - Or she could have been Dorothy's sister, following.

I think Dorothy Wattleworth (who married a William Christian and had daughter Elinor b.1773) came from Lezayre, although she married in Maughold in 1773. I couldn't find a Dorothy W bapt in Maughold.

Lezayre (IGI) has:
John Wattleworth christening: 24 March 1744 Lezayre, father:John Wattleworth; mother: Margt Quayle.
Other children, same parents, all bapt Lezayre, were:
Mary Wattleworth christening: 27 March 1737
Mary Wattleworth christening: 14 November 1742
James Wattleworth christening: 25 July 1747
Dorothy Wattleworth christening: 25 May 1751
Elinr Wattleworth christening: 5 March 1748
Margt Wattleworth christening: 30 September 1739.

John and Margaret were the uncle and aunt guardians in Dorothy's will 1781 which you summarised.

Sue