I think it's time family start checking on her every day... or if she can't rely on that, there are 'phone friends' services that will call every morning, and if you don't answer, will send help.
Or.... she could get that signal device Dr. Koop advertises. Stuff like this was the constant fear of my grandma when she lived alone, and was the only reason she packed up an moved to an assisted living facility.
The signal device I saw in advertisements, costs over a thousand dollars. A no-frills cell phone is around $20 and a calling card every few months, another $20.
My husband's grandmother had an arrangement with her neighbors. In the morning after she got up she would raise the blind in her bedroom that was on the frontside of the house. She would put it down in late afternoon to block the sun and let them know she was still ok. Her neighbors would look to see where the blind was and could then determine how she was doing that day. If it was up or down at an inappropriate time they would call to check on her. No answer of her phone and the rescue squad and family were called.
Grandmother had diabetes but was able to retain her independence for a number of years with this system. How blessed she was to have such kind caring neighbors!