My 87 year old Mom who is very sharp with everyday life has recently been seeing people sitting on her couch. She's certain they're real but can't figure out how they got into her house with the doors locked and the alarm set. Her daughter died over a year ago and she still can't believe it. She does not take any sleeping pills. The people she's seeing are complete strangers. Any suggestions?
Hallucinations are fairly common in dementia, but in most types of dementia they come late in the disease. One type where hallucinations may be the first symptom is Lewy Body Dementia. I'm not suggesting you mother has this, but if it continues and other more temporary causes are ruled out you might want to have a look at LBD symptoms.
In any case, consulting a doctor is the first step to take.
My Dad was recently seeing insects in his home and in his food. Turned out Dad had a lung infection, he's on antibiotics and slowly the bugs are disappearing.