In summary, yes, and yes.
A stroke can injure parts of the brain involved in keen awareness of the surroundings, spatial perception, and cognition. If any of these aspects of
brain functioning are damaged, the person often loses their ability to function normally, or to adapt to any small changes in environment. It is quite frequent, as the brain ages or gets damaged, for people to become confused, hallucinate, etc., particularly when it gets into evening or nighttime hours, or if they are in strange surroundings. Also, these people tend to lose their standard sleep/wake cycle patterns, and can be up at night with paranoid delusions. A classic example would be an elderly stroke victim complaining that "there are people in the house who are stealing my things".
Fortunately, you can help. First, you can try regulating the environment, keeping her in a very comforting, stable environment. You can try to regulate her sleep/wake cycles by encouraging her not to take naps, to make sure she voids all urine before going to bed (to minimize nighttime waking to use the bathroom), and possibly even using gentle sleep aids to help her sleep at night.
Additional steps, if these initial steps fail, would include seeking the help of a Psychiatrist or starting anti-psychotic medications. Often, these medicines are very effective in cutting down on the frequency of psychotic delusions.