Update!!! I am just now watching the episode where Barnabas reads from a book how Laura died. To quote directly:
[spoiler]"Laura Collins. Died, January 25th, 1875 (I'm sure he meant 1785). Cause of death, fire." He also says that Jeremiah was very upset to hear about her death.[/spoiler]
Ah, DS - we love it - but why is it that all too often things aren't made 100%, crystal clear - not to mention why do they forget things that they'd established only two episodes prior? :-
When I'd answered earlier, I was only thinking of the scene in Ep #739 in which Barnabas tells Charity that [spoiler]Laura died in a fire[/spoiler]I'd completely forgotten about the infamous "Cousin, Uncle Jeremiah" scene in Ep #741.
But apparently Barnabas is even more forgetful than I because in Ep #739 he remembers how Laura died, yet in Ep #741 he doesn't (and I love how he remarks in Ep #741: [spoiler]"Fire. How could I have forgotten that?"[/spoiler]
). And it's also odd that while referring to the circumstances of her death, Barnabas says, "It was a sudden death. That I know. My father wrote me to say that my Cousin, Uncle Jeremiah was, was very disturbed. He said not to tell him when I returned home." Huh? Not to tell him what? That Laura was dead? That seems unlikly since I'm sure we're to assume Jeremiah was disturbed over her death. So, we're then left with the circumstances of her death. But shouldn't a man already know how his wife died? Or are we to assume that they simply told Jeremiah that Laura was dead but they refused to tell him how she died? It seems unlikely Jeremiah would accept that. But who knows? This IS the Collins family, after all - a family that seemingly has to cover up and avoid dealing with everything that's too unpleasant.
... Although, if they were no longer married, it would have been easier to get away with not telling Jeremiah the circumstances.
And if the marriage had ended in divorce, it could easily explain why 1795 treats Jeremiah as if he had never been married. Divorce, though certainly much rarer than today, did happen in the 18th century - and it surely would have been a huge scandal if it became public knowledge. And if a divorce between Jeremiah and Laura did occur, like everything else that Joshua found distasteful, it's more than likely that he would have simply considered that the marriage didn't exist from that point on and probably even made up his own history. Laura could have been sent away, supposedly on an extended world tour without her husband (actually former husband) and no one outside the family was supposed to be the wiser. It would also explain why she would still be buried as a Collins. And in that scenario one can see Jeremiah only being told of Laura's death but the family being ordered by Joshua to never speak of it or the circumstances surrounding it. That's most probably not the way the DS writers conceived it because, well, let's face it, they rarely tried to explain away any discrepencies because apparently they hardly ever realized they were creating any. We can probably be 99% certain that Jeremiah and Laura were indeed still married when she died. But there's still that 1% uncertainty with the way the whole situation is presented - and that's still enough to open the door to a bit of fanfiction speculation.