Another interesting article which may help to better understand both how to recognize and identify the attributes of Borderline personality Disorder, and which may give you some insight into what the other person is actually going through.
Borderline personality disorder (BPD) is a pervasive pattern of behaving and thinking. Behaviors such as marked impulsivity, poor self image and instability of interpersonal relationships are generally the first signs and symptoms that manifest. This is a very incapacitating disorder! People with BPD often suffer from depression and anxiety. Essential Features of Borderline Personality Disorder. Fear of Abandonment. How to help these individuals.
Source: Borderline Personality Disorder