Thank you Painterman for sharing your story.
Almost didn't post, but I have an embarrassing confession to make. I'm not an alcoholic ("just" a recovering adult child of an alcoholic) and I'm able to related to your wife's side of the story.
Not that I have ever been rude to an aging old woman with Alzheimers, but I have been triggered by things that throw me into an awful state were I'm not thinking clearly. I think Skippernlilg was correct in that it can have something to do with losing control or not having things work out the way you want to.
The strangest things can trigger a distance memory for me, I start feeling worthless, and end up sulking like a little girl again. Which isn't attractive on a 49 year-old-woman :-)
Recovery is helping me identify events that cause this and I'm trying to find more appropriate outlets for my anger.
Having been on both the giving and receiving end in similar situations, I do commend you for how you handled it. Although it is difficult in the moment, not engaging is the best thing to do. It doesn't reward the behavior and hopefully makes it less likely to occur in the future. Sort of like what you do when a toddler has a temper tantrum.
Thanks again for sharing. It helped me see myself in a different light.
Also, your mum is lucky to have you as a son. Wishing you many more lovely days on the coast with her in the future!
Warm Regards,
db