I think that you are being unreasonable in expecting your friend, however nice, to understand BPD. In my experience (been diagnosed about a year now, going through a lot of therapy at the moment - we have got to my past recently, so sounds as if I am a bit further on than you) no-one actually understands it.
Its a very very complex diagnosis and its a bit unfair to expect other people with no knowledge of this kind of thing to understand - its partly why I post about this under this name on MN, (too afraid to out myself) and why only a few exceptionally close and sympathetic friends (and not my family) know of my condition.
I've chosen for the moment not to claim DLA as we don't need the money (I know we are lucky) but if I did, I don't think I would go shouting about it to anyone. People are all very worried about money atthe moment and some people might see it as boasting - I know you don't mean it that way, but you have to think how others are going to hear it - and I know that it is dificult to do this when you are a bpd sufferer.
You are not attention seeking with your daughter - but you have to learn to be careful not to come over that way - its part of learning to live with the condition. As Iunderstand it, people with bpd like me have a very hazy sense sometimes of "who am I?", and it can be very easy to live life through other people, including your children.
What kind of psychotherapy are you getting? Is it specifically targetted at your bpd? Mine is, and ismaking a huge difference in just a year. I notice you say you are writing in a rage - the uncontrollable rages of bpd were my worst symptom and I found it very hard to keep my temper in check - but it is literally months now since I was angry in that way and it is incredibly liberating not to be at the mercy of my emotions just as much.
When did you get diagnosed? Do you know your trigger? Which of the symptoms affect you worst?
Please feel free to CAT me if you want to talk about it privately.
ANd don't feel too badly aboout your friend. You probably need to tone downthe things you tell her for a while, but she honestly can't understand!! One of the reasons that I am improving so much is that my relationship with dh is so stable (and I know I am lucky in this too - not many BPD sufferers clock up a 15 year marriage and it is all down to him!), and my dh works in a healthcare profession. But even he can't understandwhat it is like to be me and to suffer the symptoms I have.
Take care, and be in touch if you need to!