Annette - I hope I can intrigue you further. I must admit there is a background to my query. My understanding of my Double ancestors further back than my greatgrandfather Joseph Double is based on research done by many others and which can be found, as you have seen, in a number of public trees. There is also a very detailed history which can be found on Google which seems to be the basis for most of those trees. Trouble is, as I have done some of my own research, I, like you, found some anomalies that I have been trying to resolve for some time. I have contacted a number of tree owners with the aim of discussing these but have never been happy that they were presenting their own original research so I didn't get far.
Specifically, from newspapers of the period, I found a Joseph Double, born about 1809, who was transported to Tasmania in 1842 and who sent for his wife Sarah in 1852 after his sentence (all this I checked out with the Tasmanian archives). The address given for her when sent for is the address at which a Sarah Double was living, married but no husband present, in Ipswich in 1851. She is described as coming from Liverpool. The public history and some trees have a Joseph Double born Apr 1809 marrying a Sarah King (born Raydon). The 1841 census has a Joseph and Sarah, both described as born in Suffolk . So what I am attempting to do first is confirm (or deny!) my theory that this Joseph is the transported one and that his wife Sarah was from Liverpool. That would put her birth place and the death date you spotted in doubt. It would also explain why they don't appear in UK censuses after 1841 (there is a possible death date for a Joseph in Tasmania in 1883 but no sign of a Sarah death there). There is an associated mystery in that a Joseph Double (and I think it is the same one) was sentenced to transportation in 1840 but must not have gone - I've had little success with this either. Sorry if this rambles a bit but it is complicated!
Not sure either that PRs would show on reflection where she was born anyway!