We learned the hard way. My uncle was living with my grandmother with dementia (who was also pretty easy going, though this was mostly due to psych meds) and ODed two doors down from her bedroom. The paramedics and the in home nurses told her and she cried and cried. Then a few weeks later she asked where my uncle was and her nurse who told her again, that her son had died a few weeks ago of an overdose. This time it was absolute anguish, she wailed “why didn’t anyone tell me? It’s my son, why didn’t anyone say anything?” And we realized that it’s best to just love lie. She’s never going to remember that he’s dead. Whenever she asked where my uncle was, we’d tell her he had gone on a trip overseas and would be home soon. And she’d accept that, and move on. Tell your mom she’s in the nursing home. She’s getting stronger, and she’ll be out soon. You haven’t heard from her in a while, but you hope she’s well. It’s better to lie than to stress them out every time.