Hi mushu;
Although I feel she would never admit to having a disorder, is she self aware of her behavior and what it does to her romantic relationships.
The tragedy of serious mental illness like BPD is that the mental illness impacts the sufferer's ability to have accurate perceptions of reality.
If you're here because you suspect she has BPD, then it's unlikely that she has insight into the cause-and-effect relationship between her behaviors and her relationships, especially if she is not currently in evidence-based treatment.
Having more relationships, or different kinds of relationships, or closer relationships, won't improve her insight or perception.
I have heard of some pwBPD, during and after evidence-based treatment, apologizing for some parts of the past, and occasionally recognizing their parts in conflicts. I haven't heard of those apologies or realizations being 100% what we'd want/expect, though there can be improvement (especially if the non's expectations are calibrated to the fact that their loved one struggles with mental illness).
While I realize living together and or marriage may episodes increase, is there a potential for her to permanently split me after marriage as some people have described, even though she had never done this while we were together?
Sure -- there are plenty of stories here of members who divorced after being married to a spouse with BPD (whether diagnosed or not).
Changing the relationship status does not heal a person with serious mental illness.
In fact, because BPD seems to impact the most intimate relationships the most, it wouldn't surprise me for there to be more challenging and more intense BPD behaviors after marriage.
What you can change is your approach, mindset, and skillset.
...
As you ponder getting back together, what are you working on, yourself, to change your contribution to the pattern of how things went? If you're not sure -- a great place to start getting ideas is our Tools/Skills section on
Relationship Skills. Anything in there stand out to you as something you'd like to improve on?
Can you remind me if you have a therapist?