Ok, this lady has caused me many sources of frustration, so much so that I've wanted to go back in time and give her a good old shake! Beware, there are umpteen Isabellas in this story.

I've exhausted researching her and the last thing I'm needing to find is her Death Cert. She seems to vanish. She has led a very interesting life for the time that's for sure. So here goes with what I have, this will be long!
She is my 3x great-grandmother.
Isabella Anderson was born 1826 in Gamrie. Her parents were:
- Robert Anderson
- Elizabeth Ferrier (1808 - 1870)
She has a number of illegitimate children with a Francis Anderson who is very much older than her. I actually suspected incest at one point. The details of these children are;
Patrick b.1855 Gamrie
Isabella Frances b.1857 Gamrie
Margaret Ann b. Oct 1859
Isabella Frances dies in 1860. Found a newspaper report saying she ran into the fire and was so badly burnt she died a few days later. Terrible story.
Then Isabella Anderson and Francis Anderson marry in December 1859. Francis is widowed and is aged 68 whilst Isabella is aged 33! Address of Francis is given as 28 Gellymill Street and Isabella's is given as 38 Gellymill Street. I suspect this to be lies and they were actually living together, but who knows.
They then have a legitimate daughter together in Feb 1863 - Mary Frances. Unfortunately Francis Anderson dies only a few months later in the May 1863!
Isabella Anderson goes on to have another illegitimate child in 1866 in Gamrie. An Isabella.
Francis Anderson's first wife was Isobel Massie (1803 - 1842).
This couple had the following children;
Mary. 1826
Isabella. 1832
(yes, another one!) 
Margaret. 1832
Christian. 1834
Francis. 1840
John. 1842
Back to my Isabella Anderson. I have her in the following census:
1851Snubs, Gamrie.
Isabella is the daughter in law of the head here (though it is actually her step-father). A Francis Jamieson, 50, Farmer of 5 acres.
This is a large household and Isabella's grandmother Elizabeth Farrier nee Mair is here aged 73.
Isabella's occupation is down as not known.
There are 2 young children in this household. An Eliza Anderson aged 4 and a George Anderson aged 1. Wouldn't be surprised if these were 2 children by Isabella here. But can't confirm.
1861Gellymill Street, Macduff, Gamrie
Francis, 69. Pauper.
With some of his children from his first marriage.
Patrick and a 1 year old Christian who I believe to actually be Margaret Ann.
187119 Carmelite Street, Banff.
Isabella aged 45 is widowed and is a pauper.
She is living with daughters Mary aged 8 and Isabella aged 5.
After this, she disappears. I cannot find her death certificate or anything that could be her in 1881. I wonder if she emigrated, but cannot find much anywhere at all. Her name is pretty common making this more difficult.
She's a bit of a mystery this lady, and the Kirk Session records for Gamrie would probably make for very interesting reading.
I have also wondered if Francis Anderson was actually the father of all of her children or whether he just took them on? It's a bit puzzling, he wasn't a very well off man himself and to take on all those children through marriage.

If anyone could help with this last piece of Isabella's puzzle I'd be extremely grateful.
Many thanks,
Liv.
Edit: Francis Anderson's parents were William Anderson and Christian Bruce (1754 - ?)
Also, Isabella was illiterate as she was signing with 'her mark' on both her marriage cert in 1859 and on the birth cert of her daughter Margaret Ann.