Hi Ipheal and
My spouse with uBPD grabbed my cellphone when I wasn't looking over the weekend (and before it locked out) took it to a locked bathroom and proceeded to look through all of my emails and text message history.
My understanding of this disorder, is that this behavior is an expression of one of the criteria descriptions for the diagnosis of BPD: "(1) frantic efforts to avoid real or imagined abandonment." Even though you may do nothing to give her cause to think that you mean to abandon her (i.e. via infidelity), she continues to *imagine* it. And so she may be convinced (by her disordered feelings/thoughts) that you mean to abandon her and she is desperately seeking evidence to justify her feelings.
She did not find much of what she was looking for (she has made baseless accusations of infidelity), but noticed I have withheld details of conversations I've had with people (specifically my family and friends). Obviously she became incredibly upset and angry. This was mostly deliberate, with the goal of avoiding triggering behaviors and encounters (even if we were talking about the same subject), but in her eyes now I am lying to her by omission and am "a liar." On a few occasions I did honestly forget to mention things, but it was wasted air trying to explain that.
Ultimately, it doesn't matter to her whether or not she finds evidence; she is acting on her feelings (for people with BPD [pwBPD], feelings = fact) -- consider another diagnostic criteria "(4) impulsivity... ."
One perspective is that for pwBPD, it is preferable to believe that you are doing something to justify how they are feelings (i.e. fear of abandonment) than to consider that there is something wrong with them that causes them to feel this way without justification. That is, it is preferable to believe something is wrong with you than with themselves; this is a defense mechanism/coping method - don't take it personally. But also, don't try to talk them out of being disordered.
Incidentally she deleted our entire message history in the process, so I have no way to verify what I might have said to her (and which in review would not paint a nice portrait of her).
By deleting your message history also allows her recollection to be just as valid as your (i.e. "he said/she said".
The things is, you both want your perspective and feelings to be heard and validated. However, she is disordered. And you are not. So there will be a discrepancy between the two of you. She may have refused to see a therapists -- don't discount that you would benefit from one yourself.
In the rational world of a relationship she is correct, I would not and should not withhold information from her. It's almost impossible for me to find a way to explain (how do you politely say, "well you were raging at the time and I didn't want to worsen things", and now she has a trust issue with me even in her normal emotional state.
She is going to have a trust issue with you simply because she has this disorder.
My understanding is this... .to more connected they feel towards you, the more familial your life with her becomes, the more her disorder will manifest. Pay attention to occasions and dates of significant family importance (to her) -- those are occasions when she is most likely to act on her disordered feelings. Think: anniversaries, birthdays, family holidays, etc... .
I did apologize and say I should not withhold details of conversations like that (and I decided I won't do it anymore regardless of consequence), but now I look like the crazy person who is acting erratically and unpredictably. Now if I miss a phone call from her, I get the "what are you up to now, I don't know what you are planning" treatment. So it has fed the paranoia quite a lot.
I'm not saying this is a good arrangement, but it helps her to maintain the believe that the problem resides in you. Because as badly as she treats you when she believes you have wronged her, she is likely to criticize/berate herself to the point of depression/suicidal ideation when she considers that the problem is with her.
I hope some of this helps.
Best wishes,
Schwing