Dates and names and all the details you have go a long way to help find more info! I was looking at your thread yesterday but there just wasn't enough there (when and whom Eliza married and when she died and her age at death, just for starters).
An 1809 baptism would fit with an 1833 marriage. Age 73 at death in 1880 = born about 1806 or 1807.
It does sound like the brother's info was given for her father when she died.
Are her children, in order, William, then John, then Elizabeth?
In the 1841 census there is a household in Clawton, Holsworthy registration district:
Charles Colwill, abt 35,farmer, not born in Devon
Elizabeth, abt 40, born in Devon
William, 4
John, 2
I would guess that Charles's father is George Colwill, 65, or parents John and Jane Colwill, 70 and 65, and possible brother Thomas, 50, on the facing page, although they were all born in county. So perhaps, if this is your people, they married in the bride's home location and settled where the groom's family was, making it difficult to connect her to any family in the 1841.
Or had your couple left England by 1841? Do you know when they left?
If that is the couple in 1841, a Charles Colwill was baptised in 1803 in Week St Mary, on the Cornwall-Devon border, with parents John and Jenifer (probably called Jane):
http://www.cornwall-opc-database.org/search-database/more-info/?t=baptisms&id=947199Do you know about your Charles? Any info you have about the family can help find more!
edit -- here is the 1841 couple in 1851 in Clawton, Devon:
Charles, 47, born Tamerton, Cornwall
(so this is likely his baptism, 1803:
http://www.cornwall-opc-database.org/search-database/more-info/?t=baptisms&id=3102707)
Elizabeth, 51, born Clawton
William, 14
John, 12
Mary Ann, 9
so it looks like they may just be doubles of your people.
