She already said her very first thought was to kill herself. Spiraling down a path where you think your dead son is talking to you may end with her creating a conversation where he "tells" her to die and be with him. That's probably not likely, but it's entirely possible. There are plenty of other bad situations that could come from the psychosis of truly believing a dead person is talking to you.

Again, I don't know if all that is true, which is why I keep suggesting a psychologist deals with this, not us, not some random person making a phone booth in a park.