Ellen Martin was the second child of James Martin and Mary Tingey's marriage. Both had been previously married.
Ellen was born in 1853, in Second Drove, Little Downham - North East of the main village.
She appears on the 1861 Census, aged seven, alongside her parents; half-brother William Crisp and siblings James and Sarah.
However, parish records are ambiguous after this point - Ellen is not with the family in 1871, nor is her younger sister Sarah. The baptism register does not include an entry for Sarah Martin but the bural register lists a burial on 18th November 1864 for Sarah Ann [Ellen] Martin aged nine years.
Age wise, this matches Ellen's age and would explain her disappearance from the 1871 census. However, it doesn't explain the disappearance of Sarah nor the fact that the burial entry uses both names.
I suspect that this will be another Death Certificate purchase.
19th August 1853 at 2nd Drove, Little Downham, Cambridgeshire.
25th March 1855, Little Downham, Cambridgeshire.
Seemingly in November 1864, aged 9 years.
Seemingly on 18th November 1864 at Little Downham, Cambridgeshire using half her sister's name (see above).