I demanded that I wanted to be there. She continued to refuse my support. Given how upset she was, i told her i would not come. Long story short, she sent me the details for the appointment and I'm here sitting in the waiting room.
Borderline personality disorder is the failure to separate/individuate from their primary attachment. Successive attachments recreate that failure in adulthood. The attachment bond for a Borderline is fusional and symbiotic and the struggles continue with the failure to separate/individuate from their partner, who is now the stand-in for the primary attachment- and whom the Borderline thinks is trying to control them as a parent/child dynamic.
Since this is an on-going struggle and due to the fusional nature of the bond, both parties suffer anxiety over control. Generally Borderlines attract people with ideas of reference about what the Borderline should or shouldn't do. This only adds to the powerlessness of the disorder.
Due to the "demands" from the partner, Borderlines struggle with free will. "I demanded that I wanted to be there" can create as much anxiety as the fear of the medical procedure. You can see where the argument about control would cause a dysregulation concerning the demand (or surmised attempt at control by the partner) which would then cause a struggle between who is in charge. When you demanded of her to be involved in her personal healthcare- this merely ignites engulfment.
She keeps telling me that this is "not about me" and I should give her space.
She's right. The reason that you are now sitting in the waiting room is because she's given in to her abandonment fear that if she doesn't allow you your demand, that you will leave her.
BPD is a complex thought process that involves persecution. In order to stop this cycle, allow a Borderline the ability to make their own decisions. All you have to say is: "if there is anything I can do, please let me know." The Borderline can then approach you to ask for your help.