Hey BPDlovesurvivor: Sorry about the situation with your partner. I hear how frustrating it has been for you. Is she actually pregnant or did she miscarry?
Did she receive a formal diagnosis for PTSD? Is she in therapy for it? People with BPD or strong BPD traits can get various diagnoses, depending on who they see and what they share (and what they withhold). It really doesn't matter if she has a formal BPD diagnosis. What matters is learning to use certain strategies to deal with the behaviors.
BPD tends to get passed on to someone in the family. It can be genetic, environmental or a combo.
She is who she is. You don't have the power to change her. The only thing you have power over is yourself and how you interact with her and react to her. If she doesn't admit to her problems, have a desire to change and get therapy, thing will likely remain as they are now (& maybe get worse).
We have had other disagreements over things like her 10 almost 11 year old son sleeping in the bed with her.
That situation can fall into the label of emotional incest.
There is a lot of helpful information in the right-hand margin. Certain communication strategies can be helpful and some people find that they can make a difference A good place to start is with the "Basic Tools". Setting boundaries and not invalidating are good lessons to start with.
You might consider getting some therapy for yourself. It's good to review your options with a therapist. You need to accept the reality of how life will be if you marry her and have children.