Thank you for posting the query.
These symptoms (seeing cats out of the corners of eyes) are not specific for Alzheimer's disease.
These are called as "visual hallucinations" and can occur with a variety of conditions. These include the side effect of medicines, psychiatric illness and early stage of dementia
The most common presentation in Alzheimer's disease is loss of memory. So, as long as she has fairly good memory, there is no need to worry about Alzheimer's disease.
Dr Sudhir Kumar MD DM (Neurology)
Senior consultant Neurologist
Apollo Hospitals, Hyderabad