Thanks again for thoughts and ideas - I do need them!
Like you I struggle to find more info on her. I did find another marriage record to Lewis Duval with her name as Charlotte Melvill Vincent - which I guess sort of makes sense but using variations of her maiden name(s) I've not found her anywhere else.
I've found a couple of births for a Lewis Duval both in London area 1739 and 1774 the latter perhaps more likely and a possible will 1810 Ilfracombe Devon that might be worth following up.
Time just goes when you're searching
