From Glos BMD and GR,

Dorothy Emma Mabel SMITH registered Q2 1921. Mother’s maiden name, HARRIS.

From this site,

Record_ID: 26466
Entry_Number: 197
Year: 1918
Month: Feb
Day: 17
Grooms_Surname: SMITH
Grooms_Forenames: Albert
Grooms_Age: 40
Groom_Condition: Bachelor
Grooms_Occupation: Sergeant Gloucestershire Regiment
Grooms_Residence: In France
Grooms_Fathers_Surname: Smith
Grooms_Fathers_Forenames: Robert
Grooms_Fathers_Occupation: Labourer
Brides_Surname: HARRIS
Brides_Forenames: Nellie
Brides_Age: 30
Brides_Condition: Spinster
Brides_Occupation: Domestic Service
Brides_Residence: The Scowles Coleford
Brides_Fathers_Surname: Harris (deceased)
Brides_Fathers_Forenames: James
Brides_Fathers_Occupation: Farmer
Licence_or_Banns: Licence
Date_of_Banns:
Signature_or_Mark: Both sign
Witness_1: Doris Jenkins
Witness_2: William Court
Other_Witnesses:
Officiating_Minister: Edward H Brice
Event: Marriage
Memoranda:
Notes:
Register_Reference: P93 IN 1/12
Page_Number: 99
Parish_Chapel: Coleford

Record_ID: 45849
Entry_Number: 2331
Year: 1887
Month: Dec
Day: 14
Parents_Surname: HARRIS
Child_Forenames: Nellie
Fathers_Forenames: James
Mothers_Forenames: Ann
Mothers_Surname:
Residence: Millend Farm
Occupation: Farm Bailiff
Officiating_Minister: W Smith
Event: Baptism
Memoranda: PB
Notes: memo in left hand margin
Register_Reference: P227 IN 1/6
Page_Number: 292
Parish_Chapel: Newland

It would appear that Dorothy had 2 siblings.

Birth Registrations of 3 children:

Births Jun 1921
Smith Dorothy E M Harris Monmouth 11a 50
Births Jun 1922
Smith Albert W Harris Monmouth 11a 50
Births Sep 1925
Smith Gladys M Harris Monmouth 11a 41

and Baptisms:( all found on this site)
Year: 1921
Month: Mar
Day: 24
Parents_Surname: SMITH
Child_Forenames: Dorothy Emma Mabel
Fathers_Forenames: Albert Robert
Mothers_Forenames: Nellie
Mothers_Surname:
Residence: Sling
Occupation: Collier
Officiating_Minister: E H Brice
Event: Baptism
Memoranda:
Notes:
Register_Reference: P93/1 IN 1/10
Page_Number: 8
Parish_Chapel: Coleford

Year: 1922
Month: May
Day: 30
Parents_Surname: SMITH
Child_Forenames: Albert Walter
Fathers_Forenames: Albert Robert
Mothers_Forenames: Nellie
Mothers_Surname:
Residence: Sling
Occupation: Collier
Officiating_Minister: E H Brice
Event: Baptism
Memoranda:
Notes:
Register_Reference: P93/1 IN 1/10
Page_Number: 26
Parish_Chapel: Coleford

Year: 1925
Month: Sep
Day: 8
Parents_Surname: SMITH
Child_Forenames: Gladys May
Fathers_Forenames: Albert Robert
Mothers_Forenames: Nellie
Mothers_Surname:
Residence: Sling
Occupation: Collier
Officiating_Minister: E H Brice
Event: Baptism
Memoranda:
Notes:
Register_Reference: P93/1 IN 1/10
Page_Number: 61
Parish_Chapel: Coleford

Mike

This must be Nellie (Ellen) in 1891,

GR 1891 Census, Millend Farm, Newland

James HARRIS, head, Mar, 35, Farm Bailiff, b. Glos, Newland
Ann, Wife, Mar, 32, Heref, Goodrich
Annie, Daur, 9, Glos, Berry Hill
Walter, Son, 6, Millend
Ethel, Daur, 5, Millend
Ellen, Daur, 3, Millend
Lilian, Daur, 2, Millend
Arthur J, Son, 7m, Millend

This looks like her in 1901,

GR 1901 Census, Milkwall, Pingrey Farm,

Alfred GODWIN, Head, Mar, 32, Farmer, b. Glos, Coleford
Annie, Wife, Mar, 32, Glos, Coleford
Edith, Daur, 2, Glos, Coleford
Levi, Son, 9m, Glos, Coleford
Ellen HARRIS, Serv, Sing, 13, General Domestic, Glos, Newland

In GR 1911 Census, Thamesfield, Maidenhead,

Fredric DOUGLAS NORMAN, Head, 54, Mar, Solicitor, b. Richmond, Yorks
Elizabeth Mary, Wife, 48, Mar, Cheltenham
Doris Violet, Daur, 16, Sing, Dulwich, London
Charles Acheson Manley STANDFORD, Visitor, 24, Sing, Earls Court, London
Nelly HARRIS, 23, Sing, Cook Domestic Servant, Newland, Glos
Lizzie WHITE, 24, Sing, Housemaid, St James, Gloucester

Albert Robert SMITH's Army records are on Ancestry + Members Trees

Joined 29/30 January 1897 aged 19 years 4 months,
born Westbury on Trym.

He was 5' 5" tall, Chest 33 - expanded 34 and a half
Fresh complextion, blue eyes, brown hair - tatoo left forename

says he married

Nellie HARRIS, St John's Coleford, 17 February 19.. (living at The Scowles, Coleford

etc etc

father: Robert SMITH, Brook Cottage Westbury on Trym, Deceased
Mrs SMITH, living in Westbury on Trym

1881 Census, Westbury on Trym, Glos

Brook Cottage

SMITH

Robert - 65 - Farm labourer, born Glos, Shirehampton
Ann - 42 -wife Laundress - born Shirehampton, Glos
Eliza E - daughter - 6 - born Westbury on T
Arthur - 5 - ditto
Albert R - 3 - ditto

Thank you so much everyone for this info. I had been going round in circles. Impressed with responses and speed of responses.