If your Aunt's behavior has changed, take her to her primary doctor and ask that she is tested for an unitary tract infection [UTI].... such infections can cause elders to become upset, rude, and even violent.
Yep, that was my first thought too - a sudden change in behavior/mood with my MIL almost always signals a UTI. Pretty easy to diagnose, and once the correct antibiotics are on board, the turn around back to her normal self is usually pretty swift.
Get her checked if possible to rule that out, then you can move down the list of other options.
It could be more serious. Have her checked out by a doctor. I heard of a similar situation where there was a major change in mood, and it turned out to be a mini stroke.
Get her checked if possible to rule that out, then you can move down the list of other options.