For some reason I remember 1837 as the "original" date of Josette's death. No idea what episode or statement in canon supplied that date. I don't remember the episode you mention at all. It must be from the Laura story?
I've been watching the pre-Barnabas episodes and in one of episodes following Vicki's arrival at Collinwood, they show a page in the Collins Family History, with a sketch (presumably of Josette) and the words "Josette Collins (1810-1834).
At this point, they are still going with the original backstory of Josette having come from France in 1830 to marry Jeremiah, whom Elizabeth says was her's and Roger's great-grandfather.
I've always wondered if Josette was supposed to be their great-grandmother? Or was she a second wife? At any rate, this was before they invented our gentleman vamp. lol