Because some people are too retarded to understand this on their own, I feel the need to explain it.
You cannot know (without professional input) if a person has any particular mental illness because THE HUMAN MIND IS EXTREMELY COMPLEX; TOO COMPLEX FOR A SIMPLETON LIKE YOU TO UNDERSTAND FULLY.
What you perceive as "Textbook Narcissism/BPD/etc." could be a combination of any amount of COMPLETELY DIFFERENT mental ailments that combine within that person and mimic the symptoms of whatever it is you assume they have.
Get it?
Also, you have to consider whether the individual themselves is suffering from the symptoms. If the "symptoms" bring them NO distress whatsoever/bring them happiness, then they're not sick in the first place. They are simply someone whose path to happiness and healthiness is one you cannot fathom/do not condone.
Leave the diagnosing up to those who KNOW HOW TO DO IT, stupid ass.