Hi Rob,
I think on balance that Isabella is the daughter of Dewhurst Bilsbury, but of course one can never be certain. Dewhurst has a daughter living with him of the correct name and age in 1851. His name is given on the marraige cert' in 1888, and Isabella named one of her sons Dewhurst. On the birth cert' of her son, Dewhurst, she gives her former name as Miller. The addesses given for John Park and Isabella Miller on the certificate tie in with lots of other information.
The mystery is why she was known as Miller and yet was a spinster in 1864. Interestingly, one of the children listed as living with Isabella in 1871 was named as Margaret Ann Miller when she got married.
For whatever reason Isabella was known as Miller prior to 1864, it does at least provide a possible explanation as to why her father's name is not on the certificate:
1864
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Registrar: What is your condition?
Isabella: Spinster.
Registrar: What is your surname?
Isabella: Miller.
Registrar: What is the name of your father?
Isabella thinks - I can't tell him it's Dewhurst Bilsbury - what would he make of that?
Isabella: I never know my father.
1888
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Registrar: What is your condition?
Isabella: Widow.
Registrar: What is your surname?
Isabella: Park.
Registrar: What is the name of your father?
Isabella thinks - No problem with Dewhurst Bilsbury this time, now that I'm a widow.
Isabella: Dewhurst Bilsbury.
Possibly I'll never know the full story, but the above is looking more reasonable. If only I could find some link to Miller. But there's another twist to it!!
On the marriage cert' from 1888 the witnesses are Margaret Ann and Francis Huddleston. Ah! another Margaret Ann - what's going on here. On checking FreeBMD there's a marriage between Margaret Ann Miller and Francis Huddleston. But I've already sorted out Margaret Ann Miller - in some detail - she married someone called Athersmith. Are there two Margaret Ann Millers, one the duaghter of Isabella, and another the witness at her wedding in 1888? I haven't been able to resolve it. However, I did get the marraige cert' for Huddleston. Father's name of the bride: Jacob Miller. I can't find any other reference to a Jacob Miller - not one that fits, anyway. Margaret Ann Huddleston is "living" in Lancaster Castle Prison in 1891. They are obviously a bad lot!
Chris.