Friend recently diagnosed - I'm seeking tips for interacting

I am in a similar position with a friend of 30 years. She has not been diagnosed, but worries constantly that she can no longer remember past or even recent events. I don't really see a group that addresses concern about a friend, so I'm posting here, but please re-direct if you know of a better fit. My friend was always calm, soft spoken and even genteel in her manner. Remarkable changes: drives very fast & displays constant road rage, raises her voice in restaurants if things are not to her liking, very forgetful (cannot remember meeting places, directions to places often visited, etc.) and shows no interest in anything. I carry the full load of conversation because she has nothing to say. She never asks about my family and doesn't speak of hers unless I ask her how daughter, grandchildren, etc. are doing. My biggest concern is for my safety while driving with her. If I drive she is a constant back seat driver and makes the journey very unpleasant. I need some ideas as to how to deal with these issues and how I can possibly help her to be less aggressive. Many thanks in advance.