We recently went on a vacation that my MIL was going to go on. She got sick and could not get insurance. We had to cancel her, but we went. She is so mad at us, because I am not sure. How can we talk to her? She left lots (at least 30) nasty messages. She does have dementia and is narcissistic.
That's how a narcissistic dementia person acts. Everything evolves around her and no one can convince her differently. She is NOT capable of seeing things from someone else's perspective. So, don't waste your time. It is like walking into a wall and hoping it'll turn into a open door.
My suggestion is to ignore her nasty messages. Delete them. With dementia, she will forget the whole thing in time. Don't bring it up, don't engage when she brings it up. Just say you've got to go, then leave or hang up.
This must be very stressful for you. But you did nothing wrong. You can't help that she thinks everyone has to cater to her. Let her stew in her own anger. Don't let her drag you down. Take deep breaths. Force your mind to think about something else more pleasant.
By the way, how was your vacation?
I'd add: poor old MIL was looking forward to going on vacation with her son and her DIL. No fault of yours, but she got ill, couldn't go, and is naturally disappointed. You can sympathise with her disappointment, can't you?
What one takes issue with is her means of expressing it! - which is to blame you and your husband for daring to have a nice time without her. This is nonsense, this is the bit you can quite rightly dismiss. But that it's a pity that she fell ill and didn't get her treat... Sure, so it is.
I know its hard to deal with nasty messages. Given her condition I have to agree with countrymouse, try to validate her feelings. Let her know you understand her disappointment and hopefully next time she can join you guys again.