Millbank Prison London ( banks of Thames site of Tate Gallery today ) was the holding point before convicts were sent to Australia, so thats where I might expect to find Sarah , if she survived the trip.

1871
Sarah Lawrence abt 1847 Caldecott, Monmouthshire, Wales Convict St John The Evangelist, London

1861
Sarah Lawrence abt 1803 Caldicote, Monmouthshire, Wales Head Caldicot, Monmouthshire
Edward Lawrence abt 1851 Caldicote, Monmouthshire, Wales Son Caldicot, Monmouthshire
Elizabeth Lawrence abt 1843 Caldicote, Monmouthshire, Wales Daughter Caldicot, Monmouthshire
Mary Lawrence abt 1860 Caldicote, Monmouthshire, Wales Granddaughter Caldicot, Monmouthshire
William Lawrence abt 1848 Caldicote, Monmouthshire, Wales Son Caldicot, Monmouthshire

1851 Caldicot
John Lawrence 41
Sarah Lawrence 40
Edward Lawrence 2 Mo
Elizabeth Lawrence 9
Loneza Lawrence 5
Mary Lawrence 12
Sarah Lawrence 6
William Lawrence 3
Mary Parry 74

An inquisition taken this 29th of March 1870 at the Cross Keys Inn Tutshill in the Parish of Tidenham on view of the body of a Male Child, Unknown [William Lawrence] aged about two months

Footnote

Sarah Lawrence was tried at the Summer Assizes for the County of Gloucester 1870 found guilty of manslaughter & sentenced by Baron Pigott to 7 years Penal Servitude

Then from the Gaol Records Q/Gc6/5

Name Sarah Lawrence

Date of Admission 13/4/1870

Prisoner Number 5456

Residence Lydney, Servant

Age 24 Height - 5 ft 2 1/4 ins

Hair - Auburn, Eyes - Hazel, Visage - Long, Complexion – Fair

Other Marks – Scar Left Eye, A Mole on Neck

Cause of Commitment – Wilful murder of one William Lawrence at Tidenham on the 24th March 1870

Summers Assizes 9/8/1870

Event of Trial - Pleaded Guilty of manslaughter

Sentence - 7 years Penal Servitude

When discharged or removed- 16/3/1871 Sentury[?] of States Warrant to Millbank Prison

Previous Known Character, Habits and Connections

Church, single, Caldicott

Mother, Sarah Lawrence Caldicott, Mon

Kinvern T[?]ope Eyles[?] 20 years

Nothing previously known against her

David D