The question I have for the group is why is this continuing to happen, when I've shown her unconditional love? The second is what types of things has the group found to be helpful in trying to prevent these cycles from happening.
Hi and thanks for posting. What you're experiencing is not uncommon and I'm sorry you're going through it. I'll try to answer your questions briefly since there's much more qualified members here that could do more justice with their answers.
1) What you're giving as unconditional love and how she's receiving it could be two completely different things. Everyone here can relate to that feeling or we wouldn't be here. A pwBPD experiences everything through emotion in real time, and they're constantly seeking happiness even through their emotions can get quickly out of whack. A look, a sarcastic comment, almost anything can be perceived as a slight and kick in their fear of abandonment or low self worth.
2) To prevent those cycles from happening, you need to break the cycle. Learn to communicate in her language by validating her feelings as being genuine. Read the courses here along the top of the page to get a better idea of how to do that.
For instance, I can say to you..."I just stubbed my toe and I'm in incredible pain, I think it's broken." You look down at my toe and it looks fine, it's not even red. Most of us would react by saying, "Your toe looks fine, let's put some ice on it" or something like that. It's logical. But to a pwBPD, saying that is invalidating and offensive. So in your response, you focus on the feelings first- "I'm so sorry you're hurting, let's see what we can do to make you feel better." Then you can take a closer look at the actual problem and address it, or share your feelings in a non-threatening way. But you always have to validate the feelings first to deescalate the situation via empathy.
Not a great answer, but I hope that helps a little.