Approaching this from 2 different directions:

1) Eliminating the 1851 Mgt Bridsons as they appear in the census index:

BRIDSON Margaret 27 Braddan 2525 392 3

This MB 27 is the wife of Daniel Bridson

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BRIDSON Margaret 27 Braddan 2525 429 44

This MB 27 is married to Joseph Bridson

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BRIDSON Margaret 26 Castletown 2526 161 18

This MB 26 is married to Robert Bridson

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BRIDSON Margaret 26 Douglas 2525 153 157

This MB 26 is married to Paul Bridson

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BRIDSON Margaret J. 25 Malew 2526 81 11

This is MJB 25 b Malew with her brother William Bridson 38 b Malew (Wm was living at Silverburn in 1841)

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BRIDSON Margaret 23 Braddan 2525 434 88

This MB 23 is an unmarried servant b Malew in household of a clergyman+his family.

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BRIDSON Margaret 23 Marown 2523 284 60

This MB 23 is wife of Thomas Bridson

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BRIDSON Margaret 22 Santon 2525 496 6

This MB 22 is an unmarried servant b Malew in household of Robert Moore

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Apart from 2 servants (so parents unknown) ages 22 and 23, all the others have Bridson as a married name ---- except MJB 25, daughter of William Bridson and Eleanor Radcliffe.

All the children of WB+ER have baptism entries in the IGI except Margaret, but the 1841 census entry for the family clearly shows a daughter Margaret age 15. Her next older sibling Robert was baptised Nov 1822. Her next younger sibling John Saml Bridson was baptised Sept 1828.

In 1851 Margaret is living with her widowed brother William at Ballachrink, and in an adjacent property at Ballachrink are her parents with their 2 youngest children plus 2 grandchildren (Samuel and Elizabeth Bell).

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2) Margaret Kennaugh nee Bridson's ages from censuses:
1861--37
1871--46
1881--57
1891--66
1901--76
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If she was the daughter of William Bridson and Eleanor Radcliffe of Ballachrink (close to Silverburn) Malew:
1841--15
1851--25
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As Averil says, the burial index has Margaret's age as 77 in 1903.
Finding Margaret in 1901 is the best clue because she states that she was born in Silverburn and that her eldest daughter, Ann, was also born in Silverburn. But she gives the birthplace of a younger daughter as Castletown.

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1901
England, Yorkshire, Templenewsam 3/25
Craig Mona
Transcribed by Ancestry as KENNUGH
R Haste Carr head 36 manufacturing engineer b Bramley, Yorks
Annie Carr wife 40 b SILVERBURN, IOM
Margaret Kennaugh mother in law wid 76 Own means b SILVERBURN IOM
Elizabeth Kennaugh sis in law unm 34 dealer in surgical appliances b Castletown IOM
1 servant
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The Silverburn birthplace suggests an inland farming family rather than the family of a mariner (John Bridson and Ann Cringle)---I'd expect them to live close to the sea.

Jean C