There are no specific guidelines about when to talk about end of life issues with someone who has a life threatening illness but here are some ideas to consider ---
Everyone has the right to be told they can’t be fixed, to be given the opportunity to address the “loose ends” of their life.
To be told you have a serious illness with dying at the end, your journey now is to proceed as if you've been given a gift, a gift of time.
Deciding not to “tell mom she can’t be fixed" takes away that gift. Who are we (yes, even family) to determine what a person needs to or does not need to know about themselves?
What a person does with the information is also their choice. Most people will react the same way they have reacted and dealt with every other challenge in their life. A person who runs away from challenges will be in denial. A person who is a fixer of challenges will take charge of the direction they choose.
I find it sad when no one will be “real” with a person who is facing the end of their life. Most of us are uncomfortable talking about or even acknowledging decline and the evidence of approaching death but that need not stop us from trying.
The depth of our relationship with the person with a life threatening illness will determine how openly we discuss end of life with them. This is not a time for games that all is going to be okay, “we are going to beat this enemy.” Instead, it is time to talk about love and memories, fears and concerns.
If you are part of a family dealing with the challenge of a loved one dying you can and should begin a conversation with other family members at any point from diagnosis on. Bring out the possibilities and discuss them. Actually, we should all have these kinds of conversations before we are faced with them.
If a casual friend, neighbor, or church member is dealing with a life threatening illness you probably want to wait until they begin a conversation about their life situation. If anyone opens the conversation door don’t hesitate to begin listening and offering information. Sometimes it is easier to talk about these matters with someone not as close to us as family.
Something More... about The Challenge of a Loved One Who is Dying
I wrote a booklet called A Time To Live: Living With a Life Threatening Illness when my step-father was diagnosed with lung cancer. It supports the person by addressing issues of comfort, nutrition, and sleep as they relate to the palliative care patient. It provides guidance to help them live the best life they can within the confines of their body and disease. The family should have a copy of GONE FROM MY SIGHT: The Dying Experience so that they can understand and watch for signs that the dying process has begun and what to do when that happens. Both of these booklets are in the End of Life Guideline Series bundle.