she will make faces of absolute disgust. She will tense up her entire body as if she has just gazed into the depths of hell and seen the face of the devil himself. It is a huge production, and it makes her look as if she is acting as intense as possible to convey to everyone in the room how she feels.
I was at a NEA-BPD Family Connections class and the instructor talked about a neurological theory suggesting BPD and autism may be linked in the brain. Researchers say that while they are different disorders, what they share in common is a deficit that makes it hard to properly interpret social cues.
When people meet my SO's D20 (uBPD -- waif-like), they wonder if she is on the spectrum. I sometimes wonder if she struggles with both ASD and BPD (Her brother is ASD and her mom is BPD).
Obviously there's a lot of variability when it comes to mental disorders .
At the very least, your ex does not seem to be socially skilled. That's hard for kids, especially middle schoolers.