Sorry late on this one….hope issues have moved on a bit…
inhibition is one of last bits of brain that develops, in late teens to early twenties- hence the number of idiot young drivers/ violent offenders/ drug tacking etc
it is also the first bit of brain affected by cognitive decline.Your mum has a diagnosis of dementia. That will mean the social norms surrounding inhibitions are not working.
She may well have often have thought that op didn’t do things she liked, as parents we all do, but she’ll now just blurt whatever comes into her head out loud. Sadly, this will get worse.
add to that, as others have said, many dementias can cause delusional thinking, especially paranoia or suspicion…and there you have it. Sadly, again it will get worse. Especially if it is Lewy body dementia.
depression is also massively common with dementia. And massively under diagnosed with dementia patients. Might be worth talking to her psychiatrist about this.
your mother has a terminal illness. Brutally, and Sadly her brain is dying. The very structure of her brain is changing. And the results are not limited to the benign wandering, forgetful granny that media seems to paint. In my relatives case they experienced violent x- rate horror level hallucinations, constant paranoia delusions, became increasingly violent and aggressive ( ages 86 after a lifetime of gentle personality). They had to be sectioned under mental health act.
These behaviours you’re seeing is mostly likely, in fact an almost inevitable, factor of her declining neurological pathways.
Her friend needs to be taken to one side and told this is what dementia does, her friend needs to know she’ll be coming out with increasingly bizarre stories if friend sticks around long enough.
Arguing or disagreeing with someone who is experiencing delusional thinking, is not the best way to deal with things. Helping them to validate their reasoning can help…asking why they think this or that, why would that person ( you in this example) do that if they love you etc can help to pull someone out of that delusion. But eventually it’ll come down to distraction, steering conversations to other topics…having a close friend “ indulge” these delusions is not good for your mother as she’ll reinforce the delusions.
you can gently try to challenge mum on what she said to friend, you’ll probably ( if you normally had a good relationship pre dementia onset) illicit an partial apology or at least a reason so you know she isn’t hating you, rejecting you or completely unappreciative. But sadly it’ll be short lived probably, before her lack of inhibitions exhibits itself in something else. Remember all delusional thinking has to be based on a core element of reality. She is lonely, you’re a constant- and sadly that means you’re a target for her delusional thinking to pivot around. It’s not you. You are going to be put in this position again and again sadly…( hopefully with more understanding mum friend 🤦♀️🤷🏼♀️). You’re going to have to rely on remembering what mum would have done or said prior to dementia and knowing that’s your mum. The person she’s becoming is less and less the mum you know and love.