Hello and welcome Pink! I'm so sorry you're going through this. There's a huge learning curve involved with BPD and you're in a position that so many of us have found ourselves in as well- the push/pull dynamic.
It's good that you shared your feelings and started making boundaries. However, it may have come across as invalidating and caused some initial chaos. That's okay, this is a time to double down on communication.
She communicated to me that she puts me before anything else, even herself. That scares me and I know is not healthy or good for her and also know that it goes back to her struggle to see her self worth or feel deserving of love.
In your opinion, is the above statement accurate? Or is that simply her viewpoint but not really true?
She continued on to say that she now feels that she cannot share her negative feelings with me or around me for fear that it will cause me to sacrifice something which will then lead to me hating her and leaving her.
Looking at this through a BPD lens, I can see where she'd get to this conclusion. Hopefully you can see that this is not the outcome you want; the goal here is for both of you to share your feelings in a productive, healthy way. You want to know what she's feeling but at the same time, you don't want to outpouring of drama that makes the relationship unstable. It's important to express this in a validating way.
As Sinister mentioned, take a look at the workshop to study some practical skills that make it easier to communicate with validation. These techniques are not intuitive at first and take some practice. In time though, your relationship can improve and get past this if you're willing to put in the work.
Questions- do you live together permanently? Do you have personal time outside the relationship?