Just noticed this and had to respond.
I was responsible for the welfare of my increasingly ill (Alzheimer's) widowed mother. The earliest stage was, unfortunately, a combination of lack of judgement and belligerence, She refused to move closer to me or to give up her home, or to have any live-in assistance, even though she was having difficulty remembering to pay bills, etc. My visits to her were almost on a monthly basis (flying 500 miles each time). During the 5 years before she passed away, she had increasingly intensive at-home care givers come in and eventually live with her 24/7. Two years before she died, I manipulated her into a really fine nursing home. Those were the most peaceful years, her most social, her most conversational. It was as if being with her peers woke her up, and being relieved of remembering paying bills, etc. allowed her focus on creative and positive emotional pursuits like painting, which she always loved. I had some intuition that this would help, based on my research experience in cognitive processes.
(No, I don't have the studies - I trashed them from the computer the day she died).
There is a physical, emotional, and deeply psychological impact of seeing the person who you respected/feared/idolized/loved most of your life revert to helplessness. Not to mention the fear that you are staring at your future self. Three years later, I'm still wading through papers, mementos, and artifacts of her life. There isn't a day that I don't think of her.
I hope you have a network of people you can talk to, and take frequent breaks and moments in frivolous downtime or selfish passions. You should seek social work help, legal advice (do you have power of attorney?) as well, and familiarize yourself with her finances and health insurance, etc. before things deteriorate. Take care of yourself.