This is a very good question. I wish there was an easy answer, but there isn't. Every situation is different, just as every family is different.

I am an Enclara Health Hospice Social Worker and have been in the field many years. This is an issue that comes up a lot.

Your Aunt has been through some tough times, so it's my guess she can handle some straight talk. Having experienced the death of her Mother last year may have been painful, but it could also serve as a reminder of her own mortality.

She sounds very responsible and someone who truly tries to do the best for her family. You may be able to use this as a starting point for "the Conversation."

You might begin by commenting on how well she has cared for her loved ones all her life. Ask if she has ever given any thought to how her Son and grand daughter will be taken care of in the event something should happen to her.

You might also want to encourage her to consult an Elder Care Attorney, (look in the phone book, or go on line.)

 But the basics are going to be completing a will, maybe a trust for her Son, a Durable Power of Attorney to manage her finances if she is incapacitated, and a Health Care Proxy or a Durable Power of Attorney  that  designates an agent who will be the one to speak for her in the event she is unable to speak for herself regarding her choices about what type of medical treatment she wants and does NOT want.

You may be surprised at how open she might be to talking about "the Elephant in the room." Many people are relieved when they are given the chance to speak openly and honestly about end of life issues.

I would begin by bringing up the topic and emphasizing the need to have someone she can rely on to carry out her wishes.  Ask her if there is anyone she would choose. She might choose your Mother, which is fine, but do point out that your Mom is getting on in years too. If you are willing to take on that responsibility, tell her so.

She may be feeling fearful and burdened and an honest, open, loving approach is always the best way to go.

While your at it, this may be a good time to address these issues with your own Mother if you haven't already done so.

You are dealing with a tough situation and you are wise to address it before it's too late to do so.

I wish you the best.