Agree. Have seen dementia and Alzheimer's up close as well. Might not be 3 pm, but late afternoon or early evening for sure. At times, they can be deceptively normal. But it doesn't usally last long.
There are probably many factors. Alcoholism, drugs, whatever. There are also many forms of dementia, not just Alzheimer's. She sure is losing control. Which is why she limits her public appearances, I am sure.