Take steps to eliminate over-stimulation such as television, children, any noise making item, quick movements and many things going on at one time. Sometimes excessive stimulation can not be avoided. When that happens, allow your Loved One to have a quiet area to retreat to. Light snacking during the day can be helpful. Make sure that your Loved One's personal needs are attended to and that the climate is at a comfortable level.
Arthritis can be one of the most common causes.
It is always a good idea that when your Loved One first begins to exhibit sundowning or when sundowning becomes common to take them to the doctor to make sure that there is nothing ailing her. One time, we bought our kids a video game so that they had something to play with. We found that the noise from the video game would set Milly off as soon as they started playing. Providing the kids with a separate private area helped both with them as well. Mirrors also became a trigger as well as a picture of Milly's daughter.