Do you know the name of her husband? - I presume that she had a child with a different surname from the death record.
I have found some records for a Bridget Bourke -- could this be her name?
There was one Bridget Bourke who arrived 6 Dec 1854, aged 20 (this would fit your estimated birth year)
There is also a Bridget Bourke (convict) who arrived 16 Jun 1848 on the 'Kinnear' (from Dublin). She applied to marry John Bentley and then, Daniel Ryan.