There's still considerable debate in the research literature on the relationship between cPTSD and BPD, and features that distinguish each. As you note, there is a lot of comorbidity. I myself qualify for a diagnosis of cPTSD, but would never qualify for a diagnosis of BPD. Some of the symptoms you list for your ex really leave me thinking BPD.

In case you might find it helpful, here's some material from recently published studies:

"While BPD and CPTSD do exhibit overlap in the type of difficulties across affect regulation, self-concept, and interpersonal relationships, there are also important distinctions that are reflected in how symptoms manifest for either CPTSD or BPD. For example, in CPTSD, there is a persistent negative sense of self, while in BPD there is an unstable sense of self that can be internalizing or positive and may change back and forth between the two. Interpersonal difficulties in CPTSD are often characterized by avoidance and disconnection, while in BPD, they may include relationships marked by either ongoing or intermittent volatility and by efforts to connect with others to avoid feelings of abandonment (Cloitre et al., 2014). BPD is also marked by more extreme strategies to regulate affect. For example, suicidal or self-harming behaviors often result from attempts to escape from or change emotions that seem intolerable (Conklin et al., 2006)."

"...These relationships with external correlates may be useful in identifying key features of each disorder that distinguish them from one another despite their substantial overlap, such as angry outbursts more often amounting to aggression or violent behavior in BPD compared to CPTSD (ICD-11 PTSD and DSO) or pervasive attempts to avoid internal and external trauma stimuli in CPTSD (ICD-11 PTSD and DSO) compared to BPD."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9107503/

"Overall results indicate that the distinction between BPD and CPTSD symptoms was strongly supported. However, our results also suggest that two symptoms of CPTSD, namely, “When I am upset, it takes me a long time to calm down.” (AD1) and “I feel numb or emotionally shut down” (AD2), were the only symptoms connecting the BPD with CPTSD constructs and potentially contribute to the overlap of the two conditions (Powers et al., 2022; Frost et al., 2020)."

https://www.researchgate.net/publication/366964802_Borderline_Personality_Disorder_BPD_and_Complex_Post_Traumatic_Stress_Disorder_CPTSD_A_network_analysis_in_a_highly_traumatised_clinical_sample

"...the DSO [Disturbances of Self-Organization] symptoms of cPTSD are consistent with the flight response, which is characterized by both unmodulated distress (i.e., DSO’s difficulty in self-calming, guilt, and sense of worthlessness) and both conscious and unconscious attempts to escape from further harm (i.e., DSO’s emotional numbing and relational detachment). Flight responses involve active attempts to restore safety by disengaging from sources of harm (e.g., fear of closeness) and distress, which are highly self-referential (i.e., associated with the DMN [Default Mode Network]) and include attempts to mobilize executive problem solving and decision-making (i.e., associated with the PfC [prefrontal cortex]). Thus, cPTSD could be understood as the maladaptive persistence of initially adaptive stress reactions that progress from hypervigilance (i.e., PTSD) to emotional/relational shut-down (i.e., DSO).

BPD could emerge as a fight response when executive control capabilities are not sufficient to sustain PTSD’s freeze/hypervigilance and cPTSD’s flight/detachment, which is consistent with evidence of diminished connectivity within the salience network and the DMN, and hypoactivation of the PfC plus hyperactivation of the amygdala, in BPD. Instead of attempts to cope by means of vigilance or detachment, BPD involves reacting in a fight mode with impulsive, disorganized, and hostile behavior in relationships and limited or no sense of self-awareness and self-efficacy. The fight reaction characterizing BPD includes a surge in bodily arousal initiated by the brain’s innate alarm system [102], and desperate attempts to prevent or retaliate for perceived or real abandonment. The alternating enmeshment in and rejection of relationships characterizing BPD also is consistent with the emotional dysregulation and deficits in executive function that have been found to occur among individuals who are experiencing disorganized attachment."

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8103648/

Thank you

It would be interesting to see if my story aligns with BPD behaviour. I haven’t really experienced something like this before, and to be honest I am really doubting myself at the moment.

Hello,

This is my first time here. Hope someone can help. I have a mother with BPD. I have been placating her for a decade pretty successfully though it is time-consuming and draining to lie so much (in order to validate her feelings etc.). I felt it was safer for me to just keep her happy and I also had a vague idea that I was being helpful to other family members by "taking a hit for the team".

But now a member of our family is moving and I knew this would trigger a nasty result for me as her primary emotional support. She laid a trap for me and I fell into it. First, she baited me by intentionally violating a few of my boundaries. I remained passive. Then she asked if I like her ... Well, I have been having some work stress lately etc. and I snapped. My entire family has collaborated to keep our true opinions from her and I just dumped the entire, cold, truth on her head. I told her she is abusive, that I know she lies, that I am not a romantic partner but a daughter, etc. I told her she isn't safe to be around, I could go on. I haven't told the truth in so long it was almost like a drug. I couldn't stop. I'm also a bit scared at how much anger this incident shows I have.

Now I am sitting here wondering if I have done something wrong. If I should apologize. She isn't speaking to me but is doing things to show she isn't speaking to me (dropping stuff off etc.) I expect there have been repurcussions from this for other family members, which I feel guilty about. I am also suspicious I am confusing guilt with just fear of when and how she will get back at me.

Is it heartless to tell a BPD person the truth? I'm so confused. My system is broken and I don't know if I want to go back. Please help.

There's a current thread on the 'divorcing' board on this subject as well. One of the admins posted a link to an older
discussion of this question you might find helpful.

"I keep having the experience where she tells me: “I am treating you so much better, and I haven’t insulted you, put you down, or name called or accused you lately.”
I let her know that it is wonderful she is feeling better though her treatment, but that as good as that is for her, on my end I would feel seen a lot more if she were to ASK ME about my experience rather than telling me how much better she treats me.
This pretty much always gets an angry response and how I am am invalidating her, and how I am ‘refusing to let me get better’."

KD, I meant to comment on this. It seems like a familiar behavioral trait where the person tell you what you're feeling and thinking and doing.

She does seem to want to be better, which is good. But she still 'needs' you to validate her reality and therefore herself. The angry response is still the behavioral/thinking problem underneath, inability to see your point of view and to empathize with your experience. Which becomes you doing a 'bad' thing to her, "refusing to let me get better". You aren't doing that, at all, of course. But it's the game of invalidation and ascribing to you motives that 'make' her respond in a certain way.

Thanks everyone for all the understanding and suggestions. I really appreciate it. Especially the reminder that boundaries are for me and not her.
At this point, there is not much new to report. Her abusive emails from last weekend, in addition to blaming me for everything that was wrong, and accusing me of many things I never did, also said she didn’t want to have anything to do with me, she hated me, she wished I was dead, and she wanted me to get out of her life, if there were going to be conditions on financial support. It gets very transactional and she seems to only want money from me.I know she doesn’t necessarily mean all of this, and I try not to take it personally, but I reach my limit at times in terms of the abuse I can take.  I haven’t responded to any of these and am just letting her be at this point, and trying not to worry about her too much. It seems best to let her be the one to initiate contact. Thanks again for all the understanding! 

Hi again
As ever grateful for a place to go and any responses I receive are all gratefully received, thank you for taking the time.
I’ve had no contact with my pregnant daughter for over a couple of months now, she has another child  due in July
I cut contact & had to block her number and email as the abuse was effecting my mental and physical health plus no contact with grandchild, her decision . Today is my grandchild birthday- Like all grandmothers  I sent cards and gifts, which arrived as they should ( tracked)
 I’ve now received a message from my son saying she will not give the gifts to the child as I haven’t given her a proper explanation about … Blah Blah Blah & that she’s unwell with her pregnancy etc etc.
I truly despise her today and regret sending the gifts as I ‘enabled her ! She’s  using the child’s birthday to further abuse both of us !
She’s not fit to call her self a Mother, in my opinion, as I mentioned before,here, I worry about her child and unborn child given her mental health. I Was going to approach SS but became too ill myself to deal with the stress and ‘upset’ that would cause and frightened it would make things worse ? .
I just feel so sad for my little grandchild, she talks to no one in the family & the only saving grace is he’s at nursery 3/4 days a week.
Very upsetting day which should be a time of love and celebration for the little one.

Thank you for the responses and interesting how your daughter is aware of her behaviour around others but happy to dish out the abuse when alone.My daughter has  no control or off  button -I suppose you can always keep the meetings to a public place !

Livednlearned,

Thanks so much.

Just yesterday, he was considering doing a 900 mile car trip, for the two of us, to visit relatives. I immediately told him to go by himself, because I couldn’t sit for that length of time.  I also told him I saw that as torture, not a pleasure trip. He was surprised. He kept insisting that I should accompany him, and I kept refusing. I felt it was important to set boundaries. I don’t even want to be in a car with him for an hour — let alone 12-15.  He eventually suggested flying. I refused again, saying I simply wasn’t up for it, but he should go ahead.  In the past, I would’ve whined and  pleaded for him not to drive, assuming he was in charge of ME. No more. After a while, the whole idea of the trip magically went away!  I think it was because he realized I wasn’t going to let him beat up on me.  So yes — I learned I could set boundaries, without escalation! I stood my ground!

I know he was appalled  when he saw that I’d love for him to go away for ten days. That would be heaven for me! 

I think he’s going to be shocked when I refuse to get in the car with him next week. He can ride with Judge Judy , like he wants to. I’ll be home, safe.