Len poses a good question. There doesn't seem to be any evidence to link Eliza Clarke b 1814 to Thomas Clark and Margaret (Cowin). Eliza isn't with them in 1841. From 1851 onwards, she says that her place of birth is IOM or Douglas, IOM.
(NB the following is speculation, not hard fact)
It may be worth looking at this family ---- a John Clark born in Scotland circa 1777 who became a grocer and wine dealer in Douglas. I suspect that his first wife was Jane Ogilvie, and that Jane may have been the mother of Eliza b 1814 (but no baptism entry in IGI). Jane died in 1817 as a 30 yr old, and she left a will. If I'm right, the will should mention an infant child or children.
A John Clark (same one ?) married a Margaret Maguire in Braddan in 1818, and I suspect that this is the family in 1841:
1841 Isle of Man Census
about John Clark
Name: John Clark
Age: 60
Estimated birth year: abt 1781
Gender: Male
Where born: Scotland
Civil Parish: Onchan
County/Island: Isle of Man
Country: Isle of Man
Street address: View image
Occupation: View image
Registration district: Isle of Man
Sub-registration district: Isle of Man
Neighbors: View others on page
Household Members: Name Age
John Clark 60
Margaret Clark 50
Eliza Clark 23
Margaret Clark 17
Elinore Clark 11
William Clark 14
Betsy Crellin 36
John Clark is a grocer.
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17 yr old Mgt Clark could be this one:
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MARGT CLARK Pedigree
Female
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Event(s):
Birth:
Christening: 21 NOV 1819 Saint Mathews, Douglas, Isle Of Man, England
Death:
Burial:
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Parents:
Father: JOHN CLARK Family
Mother: MARGT MC GUIRE
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Messages:
Extracted birth or christening record for the locality listed in the record. The source records are usually arranged chronologically by the birth or christening date.
**************************************************
********************************************
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JOHN CLARK Pedigree
Male Family
--------------------------------------------------------------------------------
Event(s):
Birth:
Christening:
Death:
Burial:
--------------------------------------------------------------------------------
Marriages:
Spouse: JANE OGILVCE Family
Marriage: 02 AUG 1806 Onchan, Isle Of Man, England
--------------------------------------------------------------------------------
Messages:
Extracted marriage record for locality listed in the record. The source records are usually arranged chronologically by the marriage date
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burial:
CLARK, Jane 30 Braddan 2 Jul 1817 OGILVIE
There's a will which might go with this:
CLARKE, Jane 1817 Braddan E 1 0106419
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JOHN CLARK Pedigree
Male Family
--------------------------------------------------------------------------------
Event(s):
Birth:
Christening:
Death:
Burial:
--------------------------------------------------------------------------------
Marriages:
Spouse: MARGARET MC GUIRE Family
Marriage: 08 FEB 1818 Braddan, Isle Of Man, England
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Messages:
Record submitted by a member of the LDS Church. The source films cannot be sent to family history centers and have limited access at the Family History Library. A family group record for this family may be in the Family Group Record Collection; Archive Section. (See the Family History Library Catalog for the film number.) These records are alphabetical by name of the father or husband.
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1851
1851 Isle of Man Census
about John Clark
Name: John Clark
Age: 70
Estimated birth year: abt 1781
Where born: Scotland
Relation: Head
Spouse's name: Margaret Clark
Gender: Male
Civil Parish or Township: Conchan
Town: Douglas
County/Island: Isle of Man
Country: Isle of Man
Street address: View image
Condition as to marriage: View image
Occupation: View image
Disability: View image
Registration district: Isle of Man
ED, institution, or vessel: 10
Neighbors: View others on page
Household schedule number: 13
Household Members: Name Age
John Clark 70
Margaret Clark 64
Eliza Looney 17
John is a grocer, wine+spirit dealer.
Margaret is b Braddan.
Eliza is a servant
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In 1861, John Clark 82 is a widower, retired grocer, living alone.
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burial:
CLARK, John 85 Braddan 16 Oct 1861
Will:
CLARKE, John 1861 Braddan E 58 0106462
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This looks a much more likely family for your Eliza (bearing in mind the family she married into) than the Thomas+Margaret Clark in all those Ancestry trees.
Worth checking out ?
Jean C