One of the symptoms of BPD is “transient, stress-related paranoid ideation or severe dissociative symptoms”. That’s a fancy way of saying that when a person with BPD is under a great deal of stress, he or she can dissociate. He or she experiences an “altered state of consciousness characterized by partial or complete disruption of the normal integration of a person’s normal conscious or psychological functioning”, as Wikipedia puts it. Translation: detachment or distancing from reality.