The first rule of dealing with an Alzheimer's patient is: Do not argue. Whatever you say will not make one tiny shred of difference to their reality. So, why do I allow myself to be dragged into arguing?
Mom was very angry with me because I did not appreciate the candles on my cake. For that matter, I didn't appreciate the cake either. She was angry that I ignored the people who took time from their day to sing me happy birthday. So, when I pointed out that it wasn't my birthday, that just made her angrier. "That woman" would have had no reason to lie to her. And, how can I argue with the proof of the cake? People don't just bring birthday cakes for no reason!
Oh, yeah! I argued. And lost. Surprise! Now, where's my cake?