After my dad's death in December 2020 my mom's health has declined from Alzheimer's. This past year she believes there are other people here.

I suggest you read this 33 page booklet (which is a free download) which has THE best information ever about managing dementia and what to expect with an elder who's been diagnosed with it.

Understanding the Dementia Experience, by Jennifer Ghent-Fuller 
https://www.smashwords.com/books/view/210580

Jennifer is a nurse who worked for many years as an educator and counsellor for people with dementia and their families, as well as others in caring roles. She addresses the emotional and grief issues in the contexts in which they arise for families living with dementia.

The full copy of her book is available here:
https://www.amazon.com/Thoughtful-Dementia-Care-Understanding-Experience/dp/B09WN439CC/ref=sr_1_2?crid=2E7WWE9X5UFXR&keywords=jennifer+ghent+fuller+books&qid=1657468364&sprefix=jennifer+ghent%2Caps%2C631&sr=8-2

She also has published a workbook entitled, “It Isn’t Common Sense: Interacting with People Who Have Memory Loss Due to Dementia.”
https://www.amazon.com/Isnt-Common-Sense-Interacting-Dementia/dp/1481995995/ref=sr_1_4?crid=2E7WWE9X5UFXR&keywords=jennifer+ghent+fuller+books&qid=1657468655&sprefix=jennifer+ghent%2Caps%2C631&sr=8-4

Here is a list of useful tips from her e-book I found to be excellent:

The “Dont's”
· Do not reason and argue
· Do not demand that they reason or problem-solve
· Do not demand that they remember
· Do not demand that they get their facts straight
· Do not correct their ideas or scold them
· Do not reorient them
· Do not think that they are being uncooperative on purpose
· Do not think that they really do remember, but are pretending not to
· Do not use a “bossy” dictatorial attitude in care
· Do not act with impatience

The Do's
· Enter into their frame of reality, or their 'world'
· Be aware of their mood or state of mind
· Use few words and simple phrases
· OR use no words, just friendly gestures and simple motions
· Do everything slowly
· Approach from the front
· Wait for a slow response
· Constantly reassure them that everything is 'OK'
· Keep people with dementia comfortable 'in the moment' - every moment
· Maximize use of remaining abilities
· Limit TV or radio programs which they may feel are frighteningly real
· Maintain privacy
· Provide a safe physical environment
Language Needs
· Use short words
· Use clear and simple sentences
· Speak slowly and calmly
· Questions should ask for a “yes” or “no” answer
· Talk about one thing at a time
· Talk about concrete things; not abstract ideas
· Use common phrases
· Always say what you are doing
· If they repeat their question, repeat your answer as you did the first time · Give them a longer time to process information
· Wait patiently for a response
· Be accepting of inappropriate answers and nonsense words
· Speak softly, soothingly and gently

Care Needs
· Recognize that receiving personal care feels intrusive
· Reassure with your tone and manner
· Do one thing at a time
· Talk through the care “play-by- play”
· Be aware of your body language and use it to communicate relaxation and reassurance
· Be sincere
· Use a soft, soothing touch
· Be aware of the individual’s unique triggers
· Be aware that a person with dementia may not accurately judge whether a situation is threatening to them
· They may respond to fear, pain or anxiety by defending themselves with what we call “aggression”
· If they become distressed, stop immediately and allow them time to calm down – don’t try to restart the activity right away
You need to change your behaviour to adapt to the dementia because the person with the disease cannot.
 
When things get to be too much for you, consider Memory Care Assisted Living for mom. It was the best situation for my mom, and I'd do it all again in a heartbeat if given the opportunity.

Best of luck.

The first thing to do is to get her in to a doctor and get an official medical diagnosis so that all other health issues are eliminated: UTI, dehydration, vitamin deficiency, thyroid problem, under- or over-medication (of prescription or OTC), diabetes, stroke, tumor, etc. Some of these conditions are treatable and could help improve her mental state. Once those have been discounted, the doctor should give her a cognitive/memory test so that it is in her medical records. At this appointment, at the check-in reception desk, ask for the HIPPA form for Medical Representative. Write in your name and have your Mom sign it. This will allow her doctor to legally discuss her private medical information with you and for you to convey actionable info about her health or problems to her medical team. If you don't do this the doctor will require that your Mom be on every call and in every discussion. If she has dementia, there is no cure. Her care needs will increase as her abilities decrease. At the same time and as part of natural aging she may also become hard of hearing, have impaired vision, incontinence, mobility problems, and more. I'm telling you this so that you can make decisions about how much you wish to provide hands-on care now and in the future. If she doesn't have many financial resources then I would contact her county's social services and request an in-home needs assessment. She may qualify for some help, like light housekeeping, hygiene and food prep. It would be helpful to consult with a Medicaid Planner for her state so that you will know the financial landscape as her care needs increase. You should never be paying for her care since it is unsustainable in the long term, and robs from your ability to pay for your own elder care needs. Finally, watch some Teepa Snow videos on YouTube so that you can learn more about dementia, and what it is and how is changes our LOs. The videos will also give you very helpful tips on how to better engage people with dementia. Dementia slowly robs people of their ability to use reason, logic and empathy -- which is what makes caring for them so challenging and exhausting. The more you know, the "better" you will be able to interact productively and peacefully with your Mom. I wish you all the best on this journey!

You appear to be in over your head. The "What to do" is make arrangements to place her in memory care so she will have people around her 24/7. There are also activities and more, she will be around people more her age, she can make new friends.

This disease has no cure, she will continue to get worse as will the demands.