What caused the dramatic change for my client last November when she was with a man having a psychotic episode and felt something dark in him, and was herself blasted with energy causing a continued struggle?

This was the consequence of a secondary effect of being in the presence of evil. Her sensing this, caused inner fear and that weakened her energy and her defenses. Not only was he heavily infested with spirit attachments, there were others hovering, wanting in on the action, because they knew a struggle was underway for control. This is much like the phenomenon of shark behavior when there is blood in the water and they become excited and instinctively become ramped up energetically, to seek the source and go on the attack. That is a good analogy for the behavior of spirit meddlers when they are attracted to dark human emotions because it represents a weakening, always, of the aura they can exploit to move in and take possession from their presence energetically within the energy system of the body. This started a chain of events in motion to worsen things over time to throw her off balance and ramp up inner fears that are a part of experiencing the normal stresses of life but can become exaggerated greatly when there are spirits on board looking for ways to worsen things and, in effect, push a person's buttons to stir up trouble.