Yes, Alzheimer's symptoms can and do worsen suddenly, once described by a man with Alzheimer's as the "come and go" disease. Although the progression of disability and memory loss in
Alzheimer's is generally slow and insidious, people with Alzheimer's may have small strokes, episodes of delirium or acute confusion in response to another medical condition or a change in confusion, disorientation or behavior as a result of an event that gets stuck in their minds. Some people develop delusions (fixed false beliefs) or hallucinations (seeing or hearing things) when they misinterpret what is happening on TV or they can't separate themselves from a fictional story. It is frightening to believe the stories on TV are happening to her in the moment. It may cause her to want to flee rather than rationally turning off the TV.
Also, most people with moderate Alzheimer's become disoriented to time - she may awake at night, responding to a dream about the TV show and leave the house in search of something she thinks she must do for the people in the story. She may be unable to take clues from the dark night that this isn't the time to leave the house.
At some point, it becomes very risky to live alone, just because these episodes of confusion, especially at night, may happen unpredictably. The hospital stay should provide an opportunity to check her for medical conditions like a silent infection that may cause delirium or a resolving small stroke, and to start a medication, if necessary, to reduce her hallucinations, especially if they are frequent and frightening episodes for her.
People with moderate stage Alzheimer's are at higher risk for delusions, hallucinations, delirium or acute confusional states in which they appear to go in and out of confusion. However, lucid joyful or pleasant behavior may occur throughout the course of the illness. Families describe good and bad days or even hours, often without an obvious trigger or precipitant like a sudden change in routine, lack of sleep, an illness or stress.
It is probably more than one problem in addition to rather than instead of Alzheimer's causing her recent sudden changes. A secure hospital environment may help her for the short term, but it is likely that she will need more supervision and reassurance in the moment, something that is difficult to arrange for someone living alone with family in another country. If travel for you is prohibitive, someone local may need to be your eyes, ears and the person to insure she gets the help she needs now.