Hi, Mr Bose,
Thank you for writing to HMC.
Considering whatever your mother in low is thinking is wrong then the symptoms you described look like false belief which in medical language is
Delusion.
the delusion may be a symptom of variety of mental disorder.
One would like to know her behavior and belief about many other thing apart from relating to you.If she is otherwise fine than delusion disorder can be the possibility. Or if she also have other behavioral problem or thinking problem then one need to rule out possibility of
schizophrenia which is not common after middle age.
One more thing is her memory. if memory problem is present then
dementia can also be the cause. Does she have
diabetes or hyper tension? if so then chances of dementia due to lack of blood flow to her brain may be the the cause of symptoms.
This all what i have discussed are common causes of false belief but it is not the complete list.
Now the best possible way to get help is to visit
Psychiatrist and trying to find out the cause of her symptoms. In this kind of symptoms
Antipsychotic medicines usually helps but this should be given under care of psychiatrist only for best possible outcome.
Hope you find this helpful.
Regards.