Her probable birth index:

First name(s) MARGARET GETRUDE [sic]
Last name DEARDEN
Birth year 1862
Birth quarter 3
Registration month -
Mother's last name -
District BRAMHAM
County Yorkshire
Country England
Volume 9C
Page 552
Record set England & Wales births 1837-2006
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Her baptism register entry:

First name(s) Margaret Gertrude
Last name Dearden
Birth year 1862
Birth date 21 Jun 1862
Baptism year 1862
Baptism date 26 Jul 1862
Baptism place Thorp Arch
Denomination Anglican
Father's first name(s) John
Mother's first name(s) Henrietta Maria
County Yorkshire (Ainsty & City of York)
Country England
Archive Borthwick Institute for Archives
Archive reference B-PR-T-A-4
Page 63
Record set Yorkshire Baptisms

A note in the margin of the register gave her birth of 21 June.
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In the 1891 Scots census she had one daughter; no entries found for 1901 or 1911 censuses:

First name(s) Last name Relationship Marital status  Gender  Age  Birth year  Occupation  Birth place

Thomas H McMurdo Head Married Male 29 1862 Retired Army Officer  Midlothian, Scotland
Margaret G McMurdo Wife Married Female 28 1863 -  England
Susan A McMurdo Daughter - Female 1 1890 - Troqueer, Kirkcudbrightshire, Scotland
Frances Mason Servant Unmarried Female 23 1868  Nurse Domestic  England
Jessie Moffat Servant Unmarried Female 54 1837  Cook Domestic  Dumfries, Dumfriesshire,   Scotland
Margaret Currie Servant Unmarried Female 16 1875  Housemaid Domestic  Holywood,  Dumfriesshire, Scotland
George Vickerstaff Servant Unmarried Male 21 1870  Groom Domestic  England
John Carson Servant Unmarried Male 16 1875 Groom Domestic  Auldgirth, Dumfriesshire, Scotland

Census details
First name(s) Margaret G
Last name McMurdo
Relationship Wife
Marital status Married
Gender Female
Age 28
Birth year 1863
Occupation -
Birth town -
Birth county -
Birth place England
Birth place other as transcribed ENGLAND
House name Cargenholm House
Street -
Town -
Parish Troqueer
City -
County Kirkcudbrightshire
Registration district Troqueer
Archive reference RG12
Piece number -
Folio -
Page -
Record set 1891 England, Wales & Scotland Census
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There are 8 McMurdo birth registration for Troqueer, Kircudbroghtshire, Scotland between 1883 and 1910.  Regrettably Margaret and her family do not appear on the 1901 or 1911 censuses.  It is too expensive to buy all those copy certificates.
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No death was found for Margaret in Scotland but this is found in England:

First name(s) MARGARET G
Last name MCMURDO
Gender Female
Birth day -
Birth month -
Birth year 1863
Age 79
Death quarter 1
Death year 1942
District HOVE
County Sussex
Volume 2B
Page 757
Country England
Record set England & Wales deaths 1837-2007

This was confirmed by the probate index.
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In the 1939 Register she was on her own in Hove, Sussex; this confirmed her birth date of 21 June 1862.
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From the Probate Index:

McMurdo Margaret Gertrude of 16 Cissbury-road Hove Sussex (wife of Thomas Hugh McMurdo) died 14 March 1942 at the Nursing Home 14 Wish-Road Hove Probate Carlisle 25 July to Thomas George Cowan bank manager.
Effects £13636 11s 11d.
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Their marriage index:

First name(s) MARGARET GERTRUDE
Last name DEARDEN
Marriage quarter 3
Marriage year 1883
Registration month -
MarriageFinder™ MARGARET GERTRUDE DEARDEN married
THOMAS HUGH MCMURDO
District CUCKFIELD
District number -
County Sussex
Country England
Volume 2B
Page 263
Record set England & Wales marriages 1837-2008
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