It turns out I had the memorial inscription all along (
!), from an English cousin who made the rounds years ago. Having found that information I was then able to fill in a lot more. Bella, by the way, was a daughter who died in infancy.
So Kite you were quite right with the 1859 death that you found. That is surely her. Even before I found the MI I had already eliminated every other possibility quite exhaustively, and then the
NBI confirmed it. Now that I'm sure what I'm looking for, maybe somebody with a public tree will have posted the cert to Ancestry. So I'm not going to rush to spend money, I'll look around first. But thanks again!
Still waiting, of course, for the 1847 cert from her first marriage. Will keep you posted.