She accused my step son of taking her car for a joy ride. He has his own car and would not be interested in her car for any reason. Yesterday she told my husband that when she came home the other day she could see the outline of someone who came in a took a nap in her bed. She said her TV was moved slightly and her alarm on the clock was changed. She gave him details......could see where someone's head was on the pillow and the outline of the arms. Nothing was taken from the home. She is a very active and independent 75 year old woman. My father in law passed away about a year ago. He had Alzheimer's. They were not close so I don't think his passing has effected her much. We are not sure how to talk to her when this happens. How many time does something like this happen before we take her to the doctor. She will think we are crazy!
Oh, just wondering if Mom-in-law are telling you these "stories" in the late afternoons or evenings. If so, she might be having the start of "sundowners" type dementia. My Dad had that, he would start to live back in the 1940's after 3pm.
We had a family friend who thought that children were playing in his house, making noise, etc. and he ran outside to get away, fell and fractured his hip. He was not able to recover, so, I'd try to ensure that she's not too frightened.
Now, if the UTI doesn't clear up the hallucinations, then this could be a memory issue.