Check medications and how she is taking them. Seek professional help for dementia and/or other causes such as a tumor from a neurologist.

Talk with her doctor. She may be experiencing serious side effects from certain meds such as pain killers.

She should be seen by a physician right away to rule out an acute cause, such as a urinary tract infection, which can alter the mental status of geriatric patients, or whether there is a chronic condition that can be causing this. Either way, seeing a physician now is the first step.