I would certainly consider that there may be a problem. Typically one would remember a movie that they saw a week ago, or even a month ago. If she is watching the same movie week after week, and, claims to have never watched it before, there may be some problems. If she is an older woman, dementia or a similar condition could be the culprit behind the issue. If it doesn’t seem like she is at the age in which such psychiatric issues would be prevalent, perhaps medications or other substances could be hampering her memory. Then again, there is the distinct possibility that she actually remembers watching the movie but chooses to say otherwise for any number of reasons.