Dixie, 

First, let me offer you my deepest sympathies! This is not an easy time for you.

Nothing you did, or didn't do, would have made any difference. Nothing anyone did, or didn't do, would have changed the outcome. Your mom had a horrible disease that ran its course. You took good care of your mom and had her in an area where she could be safe. 

I had my mother live with me for 7 years after my father died. Altho she wasn't exactly diagnosed with "alzheimers" it was pretty similar. I was working at the time.. I'd come home and find that she had left the stove on (gas stove)...she'd carry a full basket of clothes into the basement, in spite of being told I would take care of laundry...she got in a car accident because she got confused(never let her drive again)...she just started doing all sorts of unsafe things. I hired home care for her and she fought them to the point where I decided she had to go into a home where she would be watched. She was with it enough that she knew she wasn't happy. Long story short, after a year there she started to go downhill and died a lot sooner than we would have thought.She was under hospice care at the time, but, they did fail to provide appropriate care at the time and ended up answering to a complaint my brother and I made at the state level. It didn't change the outcome, my mom was still dead. BUT, I know that we did everything we could. It was just her time. 

Give yourself time to heal.