The mild intellectual disability is speculation, but something that I have wondered about from the beginning, due to her childlike affect in the Vegas Videos and her regression in general. (But that could be trauma) Obsession with Disney, maybe loving her children only when they are little and like "dolls". Her inappropriate affect in court.
I agree with you on the NPD, and that BPD is not limited to raging. But raging and non suicidal self harm are hallmarks of BPD.
As far as her challenging boundaries etc. in childhood. We don't know much about her childhood home and family dynamics to come to the conclusion that her challenging of boundaries was somehow out of the norm for adolescence. It is normal for that age group to challenge their parents and to seek independence. Also, what you and I may see as normal boundary setting , may have been extreme in her family home. And I think it was. I think her father was an Evangelical preacher. Patriarchal themes toward women and girls would have been way above the norm. Demanding submissiveness and modesty. So her normal rebelliousness would have been seen as absolutely pathological when it wasn't. It was possibly normal in a more extreme household with particular religious and patriarchal themes.
Her mother supported her relationship with an adult male because behind her father's back. (She didn't protect LT from that and did not provide adequate supervision, so there are actually poor boundaries from Mom in that particular scenario). Dad found out and was FURIOUS and responded by telling LT, a child "You made your choice, don't come back". This is an extreme and inappropriate reaction from a parent. Inadequate supervision of a minor, again. Her parents ultimately divorced due this scenario. Mom defied Dad. Apparently a 'No No".
She may be borderline, but I just don't get those vibes first and foremost. I really don't. But it very well may be.
I am sorry to hear about your family member. The one thing about BPD, loved ones will often describe it as "Feeling like they are walking on eggshells" constantly as to not trigger an episode of rage. It is awful. Another way to describe interacting with a BPD person is they act like " A toddler with fangs" but they are actually a grown adult.
Challenging of boundaries is totally normal in adolescence. The primary caregivers and parents reaction to it and boundary setting is what matters. LT's mother appeared to have NO boundaries, supporting an inappropriate relationship with a grown man when she was 16 in secret from her husband and LT's father. LT's father had a very extreme "spare the rod" reaction to it (after DT took LT across state lines and the police were involved) and effectively abandoned his minor child. We can see totally inappropriate parenting in this one incident that we "know" of.
I still get the initial impressions that I mentioned earlier. They could be wrong. I've never met her and we all know so little.
Thanks for sharing.
ALL MOO