Sorry to hear of the situation. I work with BPD patients regularly and I can help you with this question.
It is impossible to predict whether any one individual will behave in a specific way but I can tell you that it is entirely possible that she would switch back. This does not mean that she will, just that it would not be uncommon for a person with BPD to switch back and forth on multiple occasions.
Speaking purely form a hypothetical point, people with BPD often find perceived/real rejection intolerable and it is often when they are threatened by rejection that they make dramatic attempts at obtaining reinforcement - I have had many patients who have attempted to reconnect with past romantic partners when their current relationship fails.
So, yes it is entirely possible she will switch her perception of him and entirely possible she will switch her perception of you back.
You are more than welcome Harold. I suggest you take a look at something like this http://www.amazon.ca/Borderline-Personality-Disorder-Survival-Guide/dp/1572245077/ref=sr_1_3?s=books&ie=UTF8&qid=1317490386&sr=1-3
Please feel free to contact me in the future if you have further questions. Best of luck!