Strange reoccurring reactions

That is good advice. I appreciate your perspective. I love my lil sis and want to see her healthy and happy. Both in mind and body.
When these events occur I find them disturbing and surreal. They move beyond interpretation and perspective and into delusion.

My interest (other then love of my sibling and concern for her mental health) is of a curiosity and desirer to understand what is it that’s happening to an otherwise extremely perceptive and competent individual.

RacerX wrote:It seemed a good time to bring up my concerns but I was wrong. She wasn’t very receptive

I wonder how receptive you would be to someone saying they didn't agree with you, therefore you were probably not sane?

RacerX wrote:My interest (other then love of my sibling and concern for her mental health) is of a curiosity and desirer to understand what is it that’s happening to an otherwise extremely perceptive and competent individual.

This is understandable and very common in the forum. For example, people are often lacking in curiosity and desire to understand depression/suicide until a loved one starts down that path. Then, understandably, they begin searching for information, advice, etc. But, out of curiosity? No...that is well-intentioned rubbish. It is well-intentioned, as the person tries to convince themselves that a side hobby is just to better understand depression/suicide. It is rubbish, because as a family member you have the sibling as the case study. Every piece of information is evaluated against this case, determining if it might help the depression/suicide of the sibling.

And this, in my opinion, is where family members often err. Well-intentioned, they try to play the role of therapist, rather than the role of family member. They try to wear both hats. They see the mental health of the other family member and they find it difficult not to try and solve the issue. It isn't a criticism of your specific situation. It is very normal.

Right or wrong, I try to encourage family members to avoid putting on the hat of therapist or problem solver. I think it is more helpful to focus inward on your own role as sibling, which includes gaining understanding of the problem, but then to be supportive, accepting, and "nudge" as appropriate.

An update.

I made some headway in figuring out these extremely odd episodes regarding my sister.

Confabulation.

I spent a lot of time searching online after the latest occurrence. Unfortunately it culminated
in a very large and heated argument that may have severely damaged our relationship.

This particular episode took place during a conversation with her partner during a visit where my sis had chimed in to bring up how she had been abused as a child.
She went into great detail about this abuse and when I told her I didn’t recall those events she pressed and pressed as she rapidly became very angry. Again she provided sensational accounts of events (this time abuse) that didn’t happen. She even (as to prove it’s legitimacy) said to ask our Mom because she acknowledged it and they had discussed it many times. Of course when I had mentioned this to my mother she was shocked and stated non of that ever happened. Not any abuse or conversations regarding any such abuse.

Would love to hear from anyone with experience or knowledge regarding confabulation.

I want to add- I understand that those confabulating truly believe their fiction.
And because of this they are not being dishonest or misleading.
Additionally, when confabulating about something as serious as abuse the pain is real. Compounded in this situation by challenging the authenticity of her accounts.

RacerX wrote:This particular episode took place during a conversation with her partner during a visit where my sis had chimed in to bring up how she had been abused as a child.
She went into great detail about this abuse and when I told her I didn’t recall those events she pressed and pressed as she rapidly became very angry.

I have an aunt that has memories of events that never took place, primarily negative memories that portray herself as a victim in one form or another. The family has dealt with her wild, exaggerated claims for decades now.

Members of the family and the community have handled their relationship with her in various ways. Unfortunately, the bottom line is that over the years she has become largely alienated. Her own daughter and closest family members no longer have very much interaction with her. Understandably, they are exhausted, but they have all come to accept the situation in their own way. They have established boundaries that limit their contact with my aunt, so as to avoid the arguments and frustration that comes with trying to reconcile my aunts memories with reality.

With my aunt is it confabulation, dementia, a chemical imbalance, a personality disorder, brain damage, a combination of multiple issues? We don't know. No one knows. And it doesn't matter. Whatever "treatment" is available, everyone knows that it does not consist of some magical combination of words or phrases that will result in some epiphany or mental awakening for my aunt. Talking to my aunt isn't going to solve the issue. Nope, my aunt will go to her grave with these false memories, believing her life was full of negative events that never actually happened.

As a nephew, my role in the situation is "nephew". It isn't my role to try and be a therapist. That would just cause turmoil and damage relationships across and within the family. Instead, I accept my aunt for who she is, set my personal boundaries, and behave accordingly.