Sources and references for: Sociopath Diagnosis

Question:

My friend loves to date different guys, have sex with them and after a few weeks or months, dump them. She is a great liar and her mood swings are terrible. She is also an expert in toying around with men's feelings, and she loves self-inflicted pain. She loves to read people's minds and play psycho. She is always on her guard against people. This has been going on since she was a teenager and now she is 27 years old.

Is this kind classified as mental illness? Is it very serious and how can I help her?

Sources, references:

1. AMERICAN PSYCHIATRIC ASSOCIATION, WASHINGTON, DC (1994). DIAGNOSTIC AND STATISTICAL MANUAL OF MENTAL DISORDERS: DSM-IV, 4TH ED. P.645-650 Antisocial Personality Disorder.
2. Clinical experience and knowledge of Gunborg Palme, Gunborg Palme, certified psychologist and certified psychotherapist, teacher and tutor in psychotherapy.