It’s getting worse. She’s been having this delusion for months. I know you’re supposed to go along to not upset them but since this is my husband I don’t want to do that to him. Makes this extra tough to deal with. She’s angry at me now for not believing her. What should be my next step?
she could be having vision issues - flashers
I hope your husband and you both understand that this is not a real accusation, and neither of you should respond to her or feel in yourselves as though it is. If I said "your husband just beheaded all my chrysanthemums" it would be so totally absurd that you couldn't be offended or hurt by it, could you? And this fear of your mother's, because that's what it is, is just as absurd. Look on it as a puzzle, not a criticism.
For now, reassure her; tomorrow, talk to her about what she thinks is happening. Does she otherwise get on well with your husband?
Are you okay? Hope you do get to sleep, and your mother is soon feeling better.