Where she does sound like she does have some attributes of borderline personality disorder, it doesn't sound to me like she has it, at least from what you've said. I feel like there may be something wrong though. But borderlines have other qualities like: self-mutilation, passive-aggressive, constant state of chaos/crisis, and usually sees the world in a black/white or good/evil or this/that type of way (as in something is only one or the other, not anywhere in between). The reason why I said it sounds like bipolar more than borderline personality disorder is because she has the "normal" periods. Which sounds more like manic episodes.