Always good to ask each other questions and get clarifications.
The woman I found buried in El Dorado County, California, fits with the story in the obituary for Mary E Lowe Merrick (Let's call her Mary junior; Mary junior is David's sister; Mary senior is David's mother)
Mary junior obit said she moved with her parents to El Dorado, California. Ergo Mary senior would have moved to El Dorado California. Following this train of thought, I found a gravesite in El Dorado California.
The woman buried in that grave is more-or-less the right age to be David's mother Mary senior.
That is why I posted a gravesite for a woman who might be Mary Sanderlin Lowe buried in El Dorado California.
She died after 1860, which fits, because we know David's mother was alive in 1860.
Her name is given as Mary Lowe Russein.
As for the surname Russein - I addressed that in another post, when I pointed out that Mary senior was alone in 1860, so presumably William had died. Mary senior could have remarried after that. If she remarried after that, she would have died under a different surname and be buried under a different surname.
Now your cousin says Mary junior grew up in Wisconsin. I'm not sure what that means as far as Mary senior moving to California. Maybe she did, maybe she didn't.
We found Mary senior in the census in 1860 in Wisconsin, and Mary junior is age 12 at that time. So when your cousin says Mary junior "grew up in Wisconsin," that doesn't pinpoint the exact time when Mary went to California. Mary junior could live all her live in Wisconsin until moving to California with her mother in 1863 at age 15. If that happened at that time, your cousin could certainly say Mary junior "grew up in Wisconsin." At some time Mary senior could remarry (before or after move). Then after they've moved, Mary senior could die out there in 1864.
That's just one possible scenario.
At the time I posted the gravesite for Mary Lowe Russein in El Dorado, I BELIEVED the obit for Mary junior - that Mary senior had moved to California.
Now, with the news from your cousin, we're thinking that may or may not be true.
So anyway, bottom line is this: Yes I posted the grave for Mary Lowe Russein in El Dorado California as a possible (not proven) grave for David H. Lowe's mother.