Managing guilt: dealing with a loved one's endless phone calls

I have an elderly aunt with dementia who calls me around five times a day. She has three children who are closer relatives than I am, so I’m not an emergency contact. The problem is these calls often last anywhere from 1 to 3 hours. I suffer from chronic illnesses, including migraines, and even if I’m not in pain before the calls, they almost always trigger an episode.

For years, I’ve tried to explain to people around me that long conversations are a major trigger for me and that communication needs to be brief. Text messages are ideal. But having to spend an hour chatting just to set up a simple plan for the week completely overwhelms me.

Now I’m stuck with the question: How do I avoid the crushing guilt of setting boundaries with an 80-year-old who can barely write a text message? I feel like the worst person in the world. I’m not going to block her, but I do ignore some of the calls to protect my own health—which, frankly, is already fragile. And migraines are just one small part of the bigger picture.