While it is not yet clear what lead to Reynolds' death on Wednesday, questions are being raised about the possibility of her passing from a broken heart.
Reynolds and Fisher were very close and Fisher remained by her mother's side after her father, Eddie Fisher, left her mother for her best friend, Elizabeth Taylor, decades ago.
The American Heart Association recognizes a phenomenon known as 'broken heart syndrome.'
"It is rare, but you can, when you have extreme stress or grief, release hormones in your body that can affect your heart," said FOX 5 contributing medical expert Dr. Roshini Raj.
"Maybe that's what was going on as well, specifically, the functioning of the heart muscle. It's called a cardio-myopathy. It can happen very acutely, causing heart failure and sometimes death."
People suffering from underlying heart disease are at more risk of dying from 'broken heart syndrome.'