There's a wide spectrum of severity when it comes to personality disorders; just because one person with BPD is beyond help doesn't mean others are unable to lead reasonably normal lives with the disorder.
Perhaps, but uncertainty plagues all those in the borderline's sphere of influence, and more likely than not, it's a save yourself situation. If you are realistically willing to give your life for this BPD, then by all means stick it out and good luck to you. But don't presume it is any more hopeful than highly unlikely of even leading a troubled relationship. Most likely a relationship full of anguish - probability speaking.
