sisokie, I think that they are so similar that your therapist might just choose to call it Attachment Disorder. I don't know, of course, but I'm guessing.
It seems to me that attachment issues are a big part of BPD, so I have a hard time separating them. Maybe Attachment Disorder is more specified. It would be helpful and interesting for you to talk more with your therapist about this and the differences, and see what she says about it, and about you specifically