Her birth index:

This might be her, though she is Betty on the old printed index and Vera on the new online index, which adds that it is an ‘Occasional Copy: A’:

Name:                      Mother's Maiden Surname:
HORSFORD, VERA O'BRYEN     ADAM  
GRO Reference: 1913  S Quarter in HAMBLEDON  Volume 02A  Page 324  Occasional Copy: A

FreeBMD sensibly gives both entries:

Surname   First name(s)   Mother   District   Vol   Page
Births Sep 1913   (>99%)
Horsford  Betty O'B       Adam     Hambledon  2a    324a
Horsford  Vera O'B        Adam     Hambledon  2a    324
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The Banns entry, for St Peter, Cranley Gardens, Kensington & Chelsea, make is clear that the name was: Betty O’Bryen Horsford
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This then might be Betty in 1939, possibly with a couple of hidden children at Corner Green South Drive, Wentworth, Surrey (the children have to be Rodney and Sally):

First name(s)  Last name(s)  Birth date  Sex  Occupation  Marital status  Schedule  Schedule sub number
Harry C       Liddell    28 Mar 1902  M  Royal Air Force Aircraftman Service 905 S Q U A  M  67  1
Desree G      Liddell    25 Jan 1914  F  Unpaid Domestic Duties                           M  67  2
The record for this person is officially closed.
The record for this person is officially closed.
Florence M    Bower      26 Dec 1894  F  Nurse ( Children )                               S  67  5
Betty Obrian  Fletcher   30 Jun 1913  F  Unpaid Domestic Duties                           M  67  6
The record for this person is officially closed.
The record for this person is officially closed.
Aoisia        Koglowska  21 Jun 1913  F  Cook General Domestic Service                    S  67  9

1939 Ref: RG101/1889D/010/40
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I cannot find any death of any Betty O’Bryen Fletcher.

There is a report that she married a John Wilton Jerdein in 1956.  While this marriage can be found, it requires a certificate to establish that it was her.  Not sure it is worth the price.  There were no children of this couple.

This is that marriage index on FreeBMD:

Surname    First name(s)  Spouse    District    Vol  Page
Marriages Jun 1956   (>99%)
Fletcher  Betty O         Jerdein   Kensington  5c   1888
Jerdein   John W          Fletcher  Kensington  5c   1888

and this is the death index from the online GRO:

Name:                      Year of Birth:  
JERDEIN, BETTY O'BRYEN     1913  
GRO Reference:  DOR  Q3/1998 in SOUTH EAST HAMPSHIRE  (5013)  Reg H47  Entry Number 197

Fortunately there is a will for this Betty.  I have ordered it to see if there is any reference to her Fletcher offspring.  Yes there is, all three are named.  This is the right person.
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A possible Probate index, if she was the person who had a second marriage:

1998
Surname  First name      Date of probate  Probate number  Date of death    Document type   Registry
JERDEIN  BETTY O' BRYEN  09 November 1998  9852431642   22 September 1998  Grant and will  Winchester

This has been ordered to see if it contains any references to Fletcher children.
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She died at Springfield Nursing & Residential Care Home, 74 Havant Road, Emsworth, Hants.  In her will, dated 20th March 1987 she appointed as executors her husband John Wilton Jerdein and her son Rodney Stapylton Fletcher.  She added a codicil dated 20th March 1987.  She had definitely been married to Walter John Fletcher.

She also listed:

1. Her three children:
    (a) Rodney Stapylton Fletcher (above)
    (b) Sally Stapylton Maclay (already found)
    (c) Jennifer Mylne (can’t locate that married name)
2. Her three step-daughters:
    (a) Elizabeth Brown, }
    (b) Joanna Heath,    } all later revoked in a codicil
    (c) Barbara Coulton  }
3. Her in-laws:
    (a) Neil Oswell Macleay,
    (b) Nicola Fletcher
    (c) Christopher John Britwell Green - later revoked in the codicil
    (d) Allen Tarver  - later added in the codicil, possibly a new man for her daughter Jennifer - Yes!
4. Her cousin Mrs Gillian Moorhouse
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Their marriage index:

First name(s)       Wyndham J S
Last name           Fletcher
Marriage quarter    2
Marriage year       1934
Marriage Finder     Wyndham J S Fletcher married one of these people
                    Betty O Horsford
Spouse's last name  Horsford
District            Kensington
County              London
Country             England
Volume              1A
Page number         346
Record set          England & Wales Marriages 1837-2005
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I am extremely doubtful about this marriage as Wyndham refers to his wife Elizabeth’s grave, so Betty could not have gone on to a second marriage, which she did.

I await Betty’s will to see who she things she had as children.
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