How can you diagnose an episode as psychotic? what's the difference between just being poorly and having a prolonged (6 weeks +) episode of psychosis

Being psychotic: Means that in some way there was a loss of touch with reality.

Psychosis: Psychosis means losing contact with consensual reality. There can be hallucinations, but in borderline personality disorder there are more commonly delusions about others' intents toward you. Such thoughts can be very frightening, enraging, or both -- yet may not change when confronted with information to the contrary. In bpd these episodes are usually brief, but more severe than "being poorly.".