My Mom told a nonsensical/paranoid story. Anyone else experienced this?

My mom, feeling very weak in her legs, took a little flop onto the side of her recliner arm (the aide was assisting her to try and sit), hitting her tummy on the pillowed arm after a big breakfast. She proceded to vomit up her breakfast which she had just finished. The medic suggested she go to the emergency since she had two strokes in the past. (Hosptial Testing later showed no stroke or heart issues) Her BP was very high when she first go to the ER and she was given medication to lower it. Later during her stay she received Heparin, Coozar (spelling?), and all her regular meds. After she came home she continued for a few days to tell a crazy story that the hospital was really owned by a friend. (She is actually a friend who came to the house to assist that day it happened.) That is really a prison that keeps people there aganist their will. That she called the police to try to get out and that my brother in law came to visit her (he didnt). Up to now my mom (81) who has vascular dementia has never made up a story like that, only short term memory issues. The wierd thing is she is still holding onto the story as fact. She came home last friday and has been telling the story up till yesterday. I am kind of avoiding bringing it up. other than that she is with it. Has anyone had a similar situation? The doc in the hospital described it as a delerium. My mom also commented that the names of the people working at the hospital were very similar to names of people in our family. There also was a person named "Regina" working at the hospital which is the name of the person who actually came to her house to assist her and actually followed her in the ambulance to the hospital.