I have Isabella Allensby on my family tree, as a descendant of Edward Allensby my 5th Gt Grand Father.
Her name is Isabella Powley Allensby on the marriage entry in the GRO
Marriages Sep 1864
Allensby Isabella Powley Ely 3b 911
Star John William Ely 3b 911
I have assumed that the POWLEY bit of her name was her mothers family name.
I have not yet found a birth registered in Allensby Isabella Powley name , but there are female Powley registered in Swaffham around that time without a forename.
The Swaffham registration district includes Narborough
From the 1851 census Ely Holy Trinity HO107/1764 405B she was 5 years old and from the 1881 census RG11 / 3693 61 she was 38 years old so an estimate of her birth year 1844 – 1846. I nave her death as 1898
I have not yet found a marriage of Edmund Allensby her father and her mother Frances,
From 1851 census Frances was 24.
On the 1881 Census entry (RG11 / 3693 61) there is a Frances MINSBEY W Female 60 Narborough, Norfolk, England Tailoress mother in law to John Star living in the house. This has to be the same family, but the name of Frances nothing like Allensby
She could have remarried as Edmund had died in 1871
She died age 78 in 1904 as Frances Allensby which gives her birth year at about 1826.
Please let me know if you need any further informationon the Allensby line