Dementia now?...possibly...Chemical imbalance before maybe?
This could be a long rant, but I'll keep it as short as possible. My mom has had a habit of interfering in her children's marriages, pretty much since day one. She's 89 now and it's gotten to the point where she is accusing my siblings spouses of stealing things from her. (Sneaking in at night and taking them because they stole her keys and made copies)...these accusations have caused my sister to cut off communications with her. Some accusations have been absurd like thefts of her vacuum cleaner, sister and BIL sneaking in and tickling her feet at night just to taunt her. My brothers and sis think she is nuts and always has been. That this is nothing new. The problem is, I think they are wrong by putting more distance between them and her instead of recognizing there is a problem.
Sorry for the long post, I guess I am just speculating since she was doing this even in her 40's that maybe it's more than getting old. She has had mini-strokes in the last 7 years and I'm sure that dementia is also a factor. It just seems to be getting worse.