88 year old mother started hallucinations.

My mother fell about 5 weeks ago and went to the ER and they said nothing was broke and she was fine. They sent her home in pain with no meds because she refused them. The next day she was in extreme pain and her regular Dr. prescribed some pain meds. My mother couldn’t walk because of the pain and when she went back to her Dr. for a checkup about a week later they did an xray and found a fracture. Fast forward to last week and she suddenly became extremely confused and having hallucinations of people in her house, making messes, and taking over. I sent her to the ER by ambulance and after blood work and every scan they can do they said she was medically fine. They did start antibiotics the first day in case of a UTI, but the bloodwork came back normal, but 48 hours later there might have been something on the culture they said. Everyday the hallucinations got better until the fourth day when they released her and I took her home. It took a little bit to get her settled at home but then she was up cleaning because there was so much to do. My mother worked until she was 84 and is still very active and keeps a clean house. She does have macular degeneration so her eyesight isn’t the best. Saturday morning she called me at work twice because she could find her phone charger and seemed a little confused. A few hours later I went to check on her and she seemed basically fine. Had a normal conversation with me and my boyfriend and I said I would help her put her meds in her pill box since she has trouble seeing clearly. She was able to tell me how many of each pill she took a day, if she took them in the morning or evening, and could tell me what each one was for when I read the names to her. Sunday morning I get an early morning phone call that she had slipped off the bed and couldn’t get up. My brothers picked her up off the floor and she was a little confused but ok. She called me 15 minutes later hysterical that the people were back and she was locked in the house and her life was in danger. She then preceded to yell at people to get out of her bed. An ambulance took her back to the ER. She told them in the ER that she thought she was at the police station and then preceded to tell them she had been in jail all night. My mom hasn’t ever been to a jail in her life. They ran all the tests again and they say she’s fine. The nurse called and said it was probably dementia. Does it really happen that fast? Can there be some other explanation for the sudden hallucinations? She can go from totally clear headed to crazy in no time. Sorry for the ramble, but this is just coming out of left field and I’m stunned.