I am not sure what you mean by BP and BPD; they mean different things on this site and there are two forums here, one for each.

The silent treatment is not exclusive to a particular (or any) disorder; many people engage in this behavior for several different reasons. I would discuss the issue with your friend, explaining how you feel when around their behavior; they are probably not aware, thinking one thing (about themselves and how they feel) when the effect on you might be another.

http://elyntromey.com/therapyblog/?p=78