Hi damenlost,
I'd like to join Meili and welcome you to bpdfamily, I think that what you're trying to say is "is it worth it in the long run". A r/s is something that is very personal. From time to time we have people that are outsiders that are looking into our r/s and point out certain things, it's easy for them to point things out but it's not as simple as that. We can't tell you what to do, we can listen to you, provide you feedback and support you with your decisions.
You are right that you take on a caretaker role if you're in a r/s with a pwBPD, keep in mind that she has impairments, she's just wired differently. There may be a possibly that she's going to stay this way, there's also a chance that she may not, there's nothing in life that's 100%, there's always a 2% margin. A good book that's realistic about the role that we play when we have a partner that has BPD traits is
Stop Caretaking the Borderline or Narcissist.
You can click on the link and check out our book review on it, it also gives you strategies with how to cope when a pwBPD are emotionally dysregulate or baiting for a fight. From what I gather with what you shared in your post is extreme thinking or all or nothing thinking. A pwBPD really struggle with seeing the gray areas in life. Read as much as you can about the disorder, it will help you with normalizing the behavior and depersonalizing it as well.
I know that being told that you're the worst thing that happened to her would really sting, also keep in mind that feelings equals facts to a pwBPD, so she probably had very intense feelings at the moment and she's judging you based on those feelings not on facts. I mentioned earlier that things are more complicated than that, we have more parts to us, good and bad that a pwBPD don't see in us at moments where they have intense feelings. Try to depersonalize it because it's something that our pwBPD are going through at that time, try to separate yourself from her.
I know that it's easier said than done, it takes time to make changes, I think that it takes consistency, keep at it and you'll see change bit by bit over time.