There are over 150 birth records for people called Megan Williams, so identifying hers is a tad fraught.
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There is only one death of a Megan Stopford who was born anywhere between 1911 and 1931:

FindMyPast produces this, including her birth date, from some GRO files:

First name(s)               Megan
Last name                   Stopford
Gender                      Female
Birth day                   7
Birth month                 12
Birth year                  1918
Death quarter               2
Death year                  2002
District                    Bath & North East Somerset
District number             3001A
Register number             A3D
Entry number                202
Date of registration mm/yy  0502
County                      Somerset
Country                     England
Record set                  England & Wales Deaths 1837-2007

And the GRO death record, but without the precise birth date is:

Name:                Year of Birth:  
STOPFORD, MEGAN      1918  
GRO Reference:  DOR  Q2/2002 in BATH AND NORTH EAST SOMERSET  (3001A)  Reg A3D  Entry Number 202
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From the above birth date any registration in England and Wales, if that was where she was born, would have been in Q4 of 1918 or Q1 of 1919 and FreeBMD will select registrations for short periods such as that and they are:

Surname   First name(s)  Mother  District  Vol  Page
Births Dec 1918   (>99%)
Williams  Megan    Britton   Pontypridd      11a   1215
Williams  Megan    Jones     Pontypridd      11a   1262
Williams  Megan    Hughes    Bangor          11b   ___
Williams  Megan    Roberts   Merthyr Tydfil  11a   14_
Williams  Megan J  Matthews  Frome            5c   524    
Williams  Megan M  Palmer    Pontypridd      11a   1034
Williams  Megan V  Morris    Merthyr Tydfil  11a   1328
Births Mar 1919   (>99%)
Williams  Megan    Williams  Bridgend        11a   1405
Williams  Megan    Rosser    Pontypridd      11a   1083
Williams  Megan    Meloons   Grimsby          7a   758
Williams  Megan H  Jones     Merthyr T       11a   1209

Not a lot further forward!
The online GRO births are the same.
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And, from BP, her father is reported to be Arthur Reyner Williams and he married in 1910 in Cippenham dist, Wilts, one of Edith Maud Melsone and Edith Ellen Bailey  And I can’t see either mother in the above FreeBMD list.
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Not found in the 1939 Register (in 2022 when her death in 2002 should, hopefully, have allowed her record to be seen).
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Her probate index:

Surname   First name  Date of probate  Probate number  Date of death  Document type   Registry
STOPFORD  MEGAN       14 August 2002   1024688         04 May 2002    Grant and will  Winchester
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Their marriage index:

First name(s)       Michael R H
Last name           Stopford
Marriage quarter    3
Marriage year       1945
Marriage Finder     Michael R H Stopford married one of these people
                    Megan Williams
Spouse's last name  Williams
District            Marylebone
County              London
Country             England
Volume              1A
Page number         1565
Record set          England & Wales Marriages 1837-2005
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