Would still be good to confirm who she was from wills of parents, parents-in-law, and/or siblings.

Maughold par regs have the marriage dated 27 Oct 1790.

Baptisms, besides Bessy's:
Thomas son of Ewan Kneale & Elizabeth Corkill bapt 5 Aug 1792. Private baptism.
Elinor dau of Ewan Kneal & Elizabeth Corkil bapt 1 Jan 1795.
I guess she was called Bessy because her mother was Elizabeth.

There was a Ewan son of John Kneal & Bahee Curlet bapt Maughold 10 Apr 1768, but don't know whether this was him, and an Elizabeth dau of Thomas Corkill & Ellinor Kermod 22 Oct 1769. Private baptism.

An Elizabeth KNEALE was buried Feb 16 1795.
Also Elizth KNEALE buried Nov 21 1816.
Eliz KNEALE aged 79, of Ramsey, buried Mar 30 1847.

The Ramsey 1841 census might help identify the last one if she was living with one of her children. If so, that person's age could then be double-checked in the 1851 census.

Sue