In my experience people having psychotic episodes can be very logical in a twisted way. Once my cousin was having an episode. He explained to me how manna fell from heaven. {he often got very religious during those times}. He said a spout of oil shot into the sky and reformed into bread... hydrocarbons becoming carbohydrates.
Depends on the cause of the psychosis, I have a suspicion Sheila may have been addicted to cocaine which may have caused a dangerous and violent psychosis, her PS may have been secondary to this?