My Husbands Uncle Dennis Is Currently In Hospital For The

My husbands uncle Dennis is currently in hospital for the last few months with Alzheimer's (can be agitated ) 93 years old he has been known to lash out at his wife Aileen who seems to make matters worse in my opinion. She is 83 years old (Aileen ) and has an identical twin (Peggy) who has Dementia. They are both now getting forgetful but Peggy is the worst.
I brought Aileen to see Dennis her husband today with my daughter who is a 3rd year nursing student and what we both observed was a bit shocking. She had bought him a magnum icrecream on the way in and was not very nice giving it to him. She pinched his nose and slapped him a few times. I actually believe she was not aware she was doing it. His speech is slurred and he is confused but this seems to frustrate her and make her angry with him. I feel after today's visit that she should not be left alone with him as she is making matters worse. It was sad to see. I will tell her son tomorrow of my concerns but can you make any suggestions or give me some advise as old age can be complex ? Dee