I read peoples comments about the narcissism, but I need to know why mom says these hurtful things. No one believes them and you know soon I would be accused of stealing, but the other things she says, when all I do is help her and keep her company, I don't understand. I'm not yet in counseling and mom is set for neuro appt, but I now moved in to be with her 24/7 and mom says she says these things to get off her chest and not fester. I always told mom I would tell her the truth and not lie to her, am I doing the right thing?
https://www.agingcare.com/articles/how-to-handle-alzheimers-disease-lying-144204.htm
If your mom has dementia, you have to think of her saying false things about you, not as lying, but as her broken brain trying to make sense of things.
A really simple example is "the food is burned. I don't remember burning it. Laura is here. She must have burned It! Laura, you're so careless! Why did you burn my food? We can't afford to waste food!"
The understanding response to this is not I didn't burn the food, you did" which will only turn to a shouting match. Rather " oh mom, I'm so sorry the food burned. Here I'll clean that up. Don't worry, there is plenty more I can make."
There is a great woman named Teepa Snow who has some videos online with more of these ideas. You can google them.