Hi, I Have A Question About My Mother-in-law. She Is

Hi, I have a question about my mother-in-law. She is 86 and has always been very healthy. She takes no prescription medications at this time. We have noticed that she will repeat questions or tell us the same things over and over. We have also noticed that her personality has changed. she used to be very mild mannered and agreeable, she never raised her voice or got mad. She now gets angry easily and will even yell at you. She complains about being tired all the time and has stopped going to the store, to church and even to families house to visit. She cares for her deaf 49 year old son who lives with her and lost her husband about 3 years ago. Her son recently got a puppy and she blames the puppy for her being tired and not being able to leave the house. Her son takes care of the dog and has a run and cage for it to stay in when he isn't home. Should we be concerned about her behavior or is this just normal aging?