« Reply #7 on: Tuesday 02 October 12 21:07 BST (UK) »
Have you had a look at online trees (e.g. at Ancestry, just for a giggle)?
There are a few that have a Mary Axhorn born in Tiverton 1786, with parents, but no other info.
There are also some that show a Mary Ann Axhorn born 1811 and residing in England for several censuses and then inexplicably dying in Sydney NSW (where I see no record of the 1900 death). Her mother is shown variously as Mary Bettison (who would be Mary Axhorn by marriage) and Elizabeth Bettison. It's the usual dog's breakfast found in Ancestry trees. In 1841 the father, Isaac Axhorn, is in Tiverton with wife Elizabeth; the name has been corrected by an Ancestry user.
All those people might be worth contacting to see whether one of these is the Mary Axhorn in question. Of course, you might be one of those people.

I had just wondered, since not all death sentences were executed and many people were transported instead, whether that angle might be worth looking at. You didn't mention your connection with this Mary, so not sure what you might already know about Axhorns etc.
HILL, HOARE, BOND, SIBLY, Cornwall (Devon); DENNIS, PAGE, WHITBREAD, Essex; BARNARD, CASTLE, PONTON, Wiltshire; SANKEY, HORNE, YOUNG, Kent; COWDELL, Bermondsey; COOPER, SMITH, FALLOWELL, WILLEY, Notts; CAMPION, CARTER, CRADDOCK, KENNY, Northants; LITTLER, CORNER, Leicestershire; RUSHLAND, Lincolnshire; MORRISON, Ireland; COLLINS, ?; ... MONCK?