Did the doc see her TODAY after the onset of this problem, or was Alz and Dementia ruled out long ago? If this is a new development, then she needs to see the doc again. This could be a symptom of many problems, and none of us here are qualified to diagnose it.
Boy if you haven't gotten her to a doctor, I'd get her to one ASAP (like the emergency room). It could be a stroke and the longer you wait, the worse the outcome could be. Any other symptoms? It could also be a urinary tract infection as ba8alou says, but someone who's a physician needs to see her ASAP. Let us know what they find.