Okay, on the 1841 census Sarah is down as age 50 (i.e. 50-54) and born in Surrey:
https://www.ancestry.co.uk/interacti...59462569/facts
Her husband died in 1847, so she should be a widow on the later censuses if that was the right death for her.
This could possibly be her in 1851?
https://www.ancestry.co.uk/interacti...cklabel=Return
12 Ordnance Row, Lewisham, Kent
Thankful Bookenden Head Widower 89 Retired Ship Builder Kent Brompton
Sarah Crookenden Niece Widow 61 House Keeper Kent Witersham.
Surely his surname can't be Bookenden? But it does look like it.