That she has a parent with a personality disorder, is perceptive about other’s emotions, and has extreme emotional reactions all indicate that your hunch may be correct.
You sound like a very caring partner and you are wise to realize that your role is not to be the service provider to help her process her emotions, because that is hers to do alone. Should you try and function this way, your relationship will increasingly become more dysfunctional, as you realize.
As the “non” in the relationship, you need to be the emotional leader and the help you can offer is to let her deal with her own issues, but be a supportive listener.
With BPD, there is a lack of emotional development and the kindest thing we can often do is to step back and let our partners solve their issues themselves. Otherwise, it’s easy to get into a codependent cycle with them, which serves no one.
Here is an article that might be helpful:
https://bpdfamily.com/content/what-does-it-take-be-relationship