I read a recent post here that brought back a lot of memories of my ex gf who I strongly suspect had BPD (she would not seek therapy).
There were always little red flags that both she and I tried to explain away, but I remember if anything was done without her (yearly trip with the boys, a conference, etc.), she always seemed irritated in a just-under-the-radar sort of way. I told her once that it was really hard for me when I wanted to enjoy an event with friends, but felt like I was on the phone with her inevitably upset.
There was also a landmark birthday where many of my friends I've known most my life were there. The feeling was very warm from everyone EXCEPT her. She explained it away as being tired since she had been up early. I didn't push it, but I remember it really bothered me to look around that night and see the genuine looks of happiness from old friends and see her looking irritable or bored.
And I guess it just got me reflecting a lot lately. Did she feel threatened by any happiness that wasn't directly provided by her? That's so weird to me and so horribly selfish.
You've hit on a very common behavior with BPD folks. They often see themselves as the center of the world, and expect the same from others. My wife's grandmother, describing her own daughter, said it just seemed that my MIL was a three year old throwing a tantrum, and that all the rest of us were adults dancing and juggling in a circle around her, trying to keep her happy.
My FIL is an enabler, and he has accepted the MIL-centric model of the solar system. His chief complaint against my wife and I is that we do not accept that model.
I don't think it is necessarily selfish in intent. I think they are very much wounded and hurt. Drawing all that attention I suspect is an attempt to only get back to normal. I don't mean to defend it as decent, or them as innocent. I just figure the behavior is way deeper than we think, and not as superficial as typical selfishness.