only a psychiatrist can diagnose this. you cannot FORCE anyone to get treatment for anything. society cannot even force people to take meds if they dont want to. people generally are only helped by the official authorities if they attempt suicide or threaten to hurt other people. if they just go along on their merry way, not much you can do. if they have young children in danger, report them to the authorities. if you are married to them, divorce them. everyone is responsible for themselves. people who are mentally sick know they are, they often just chose NOT to get help or be seen as weak. i am sure you have options. sometimes you just have to say goodbye. sounds harsh, but life is harsh. people spend too long trying to fix other people. everyone has a right to live as they like, even if they are mentally unsound. its their life.
Borderline personality disorder (BPD) is a serious mental illness characterized by pervasive instability in moods, interpersonal relationships, self-image, and behavior. This instability often disrupts family and work life, long-term planning, and the individual’s sense of self-identity. Originally thought to be at the “borderline” of psychosis, people with BPD suffer from a disorder of emotion regulation. While less well known than schizophrenia or bipolar disorder (manic-depressive illness), BPD is more common, affecting 2 percent of adults, mostly young women.1 There is a high rate of self-injury without suicide intent, as well as a significant rate of suicide attempts and completed suicide in severe cases.2,3 Patients often need extensive mental health services, and account for 20 percent of psychiatric hospitalizations.4 Yet, with help, many improve over time and are eventually able to lead productive lives
http://www.nimh.nih.gov/health/publications/borderline-personality-disorder.shtml
Symptoms of Borderline Personality Disorder
http://psychcentral.com/lib/2007/symptoms-of-borderline-personality-disorder/
Borderline personality disorder is often a devastating mental condition, both for the people who have it and for those around them.
Perhaps shaped by harmful childhood experiences or brain dysfunctions, people diagnosed with borderline personality disorder live in a world of inner and outer turmoil. They have difficulty regulating their emotions and are often in a state of upheaval. They have distorted images of themselves, often feeling worthless and fundamentally bad or damaged.
http://www.mayoclinic.com/health/borderline-personality-disorder/DS00442
Emotionally Unstable (Borderline) Personality Disorder is a condition characterized by impulsive actions, rapidly shifting moods, and chaotic relationships. The individual usually goes from one emotional crisis to another. Often there is dependency, separation anxiety, unstable self-image, chronic feelings of emptiness, and threats of self-harm (suicide or self-mutilation). This disorder is only diagnosed when these behaviors become persistent and very disabling/distressing.
http://www.mentalhealth.com/dis/p20-pe05.html