Hi
@O&L , this is a great place for support and suggestions for help, I've found it invaluable over the last couple of years.
When she was still living at home mum became convinced things were being stolen. In her case she blamed the neighbours and was repeatedly banging on their door demanding they returned things She also phoned the police on various occasions and was convinced they were enacting 'hate crimes' against her. She would tell me what was missing and I'd try to find it. The trouble was that when I did find a missing item, a dress or a pair on sunglasses, she often didn't recognise it as hers.
Your mother may well move on to accusing someone else, but in the meantime no amount of telling her she is mistaken will work. We tried three approaches with my mum, my husband just said flat out, 'you are wrong, nothing has been stolen.' I tried logic 'In any given situation the simplest explanation is the most likely, therefore it is more likely that you've hidden or thrown that thing away rather than the neighbours, who do not have a key, sneaked in when you weren't looking and took them. The only one that sort of worked, was that of my brother, who treated her like his dog, and offered her a treat to break her from the loop of repeated accusations.
In the end mum's behaviour meant she was no longer save living alone, and she is now in a care home. Does your mother have help coming in?