It could be an antisocial personality disorder (psychopath, sociopath) because of the following symptoms:

• She is promiscuous
• She has had this kind of pattern since she was a teenager
• She lacks respect for other people
• She humiliates other people
• She does not adapt herself to the norms of society for human behaviour
• She lies
• She deceives other people just for fun
• She is irritable and aggressive
• She does not understand the serious consequences her behaviour can cause her in the future

You can help her by trying to make her aware of how her thoughts and behaviour, so normal for her, are so different from most other people. Point out that she will hurt herself in the long run, because her behaviour will result in her having many enemies.

People with anti-social personality disorder, also called psychopaths, can do much more harm than your friend. If they are in positions where they have power and authority, they may ruin the lives of lots of people. They are often very convincing and are very good at getting what they want. Sometimes the best way to deal with this kind of people, is to avoid all contact and cooperation with them.

In general, it is difficult to treat a person with anti-social personality disorder. To try to get them to understand that they are hurting other persons is often difficult, because they do not have any conscience, and it is hard to help them get one. It may have some effect to convince them that it is in their own interest to change, because their behaviour is hurting themselves in the long run.