Looking for help with a DD Mother

Hi, long time reader, first time poster.
The story is long, experience is tedious, so I will try to be as concise as possible.

My mom is most likely DD, as she thinks there is a group of evil entity that is manipulating everything around her. It started as being spied or monitored, like phone conversations or computer, then lately it manifested into everything around her, from a phone call, to even just a stranger passing her by. For the past year or so, she has started hearing the instructions of her unknown deity. At first, it felt like a safety net for her, then it turned into her driver in alternate reasoning to everything that goes on in this world. The evil doers appears to be a very specific set of people she might have dealt with in the past. She believes that this group of individuals have the power to control everyone around her to evil-ize her world. Simply put, it's her own version of "Good vs Evil" fixation. She battles against evil 24/7 now, and sounding off her ultimatum around the home she lives in.

She went to a professional before, but that was short-lived. She refused to go back or go to any professional for that matter. This also expanded into every type of doctor, so her health is deteriorating. Attempt to convince her has failed, and she strongly refuses to go seek professional help, even if it's just a regular doctor visit. We sense that if we escalate it anything further, something might snap.

I am at wits end. It's almost 10 years since I was made aware of her condition. No logical reasoning had ever gotten through to her, and now she is using her deity as her absolute reasoning, as in, no discussion from us can go beyond 2 sentences before met with an absolute 'shut up'. I feel like she has reached a new stage, and it is progressing into something that requires attention.

I have no idea what to do.....any advice, tips, experiences would be much appreciated. Thank you.