How do you politely inquire about someone to a third party if there is a possibility that they have died?

About 18 months ago I was in contact with a woman in her 80’s regarding family history. We passed dozens of emails back and forth for a while but then both got involved with other projects. I had not heard from nor tried to contact her in over a year. Attempts to contact over the past month using both email addresses she used in the past have been unsuccessful. While not in ill health, she was getting on in years and there is always the possibility she had passed away. I ran a quick email search for obits in her town to no avail, fortunately.
I have the email addresses of a couple of relatives that were also involved (her passing on information to all of us) and am considering contacting them.

I feel like the guy pulling the cart full of plague victims in The Holy Grail was probably a little too blunt in asking “Is ‘E dead?” so just how do I inquire as the the well-being of my original contact without just coming out and asking if she has died?