The trap I fell into was thinking that if I treated people well, they'd automatically return the favor.
Especially not a BPD. They are very jealous of the peace that people who love themselves have. It drives them up a tree. In my personal case, my family member that suffers is a lot more creative than I am, but doesn't do anything with his or her abilities and then thinks I'm trying to show him or her up when I win an award or something.
The thing to remember is that they aren't totally in control of their actions. The common thought is that it takes a combination of drugs and therapy to deal with the disease.
edit: check out the symptoms in the above book by clicking on the search inside link. It's the fifth or sixth page in.