I have a 96 year old grandmother who has deteriorated rapidly in the last 6 months. Her mind has suffered the most. Trying to understand what to expect?

She is downright mean, and violent. My question is whether there is a correlation between this mental deterioration and pending death or if there is little relation. Physically she is feeble, but mostly fine. She requires so much time and effort from our family and she was once so regal and beautiful that this process seems cruel. I just hate to see her this way. Not wishing her to pass, but trying to understand what to expect?