BPDFamily.com

In regards to my experience with the exBPD SO I would say it was almost scary how she could act then march into work, or how she would be able to function at work then what she would do as soon as she got off.  As far as the high or low being static, I guess it depends most on the BPD in particular and their situation as much as anything.  I think she was hanging on the edge of being a High functioning BPD, only for the fact that she was able to go to work most of the time.  I definately was able to see several traits of the different personality disorders in my exBPD SO,she would shuffle between Narcissistic and Histrionic with ease at times.  She loved the attention when higher up men at work would say anything to her, she was almost giddy with glee.  And then she would make sure everyone she knew was aware of how great her new car, clothes, vacation was soo much better and greater than anyone else's.  In regards to the black and white thinking, when I first met her she told me about all the bad things her ex husband had done: stole money, cheated,   she was able to tell such a good tale I thought maybe she was embellishing some, but that most of it maybe true.  Over the course of a couple years her ex husband went from being the meanest person in the world to being someone she talked about watching her house while she was out of town, I very seriously doubt now that he ever talked to her after their divorce, I believe it was her way of splitting him from black back to white over the course of a few years.  I kick myself these days because all of this stuff certainly didn't start coming out to where I could see it until way after she had me hooked in.  I appreciate all of your responses with this very much, Thanks.  

Yes, I experienced a similar story, she was very good until I moved in with her.  Then within the first few months things started to deteriorate and when our first household stress came on (I got laid off) she went crazy.

She was high functioning and hid it very well at work.

I think the idealization phase allows them to control the worst of BPD at the beginning.  And her ability to control herself at work always amazed me and this was a contentious point when we went to therapy, I felt that if she could control it 90% at work then perhaps expecting her to control it at home was realistic... .  it wasn't.