Is this one or multiple personality disorders?

I have a sister who seems to meet multiple descriptions I have read on personality disorders.

History. She found my mother dead from a suicidal gunshot at the age of 8. She was in shock for a year and blamed my father for her suicide. She has spent much of her life alone or in stormy relationships that ended dramatically.

She exhibits these following Borderline Personality traits. Her relationships with others are intense but stormy and unstable with marked shifts of feelings and difficulties in maintaining intimate, close connections. She constantly manipulates family and friends and often has difficulty with trusting anyone. She is also emotionaly instabile with frequent shifts to an empty lonely depression or to irritability and anxiety. She often shows inappropriate, intense anger with tantrums, constant brooding and resentment. There are also identity disturbances with confusion and uncertainty about goals, career choices, friendships.

She also exhibits Paranoid Personality traits. She prefers to be by herself. She distrusts everyone and is constantly suspicious that people are out to get her personally or professionally. She avoids or destroys relationships and frequently interprets hidden and hostile meanings or intentions into the actions of others. She is quick to challenge loyalties of loved ones and what few friends she has, and is often cold and distant. She constantly shifts blame to others and carries long grudges or is completely unforgiving.

I am hoping you can provide me with some insight about her condition or help me to cope with her.

[Roger Gould, M.D.]

Your sister is a desperately unhappy woman, suffering a lot, and in the end, is very difficult to be with or sustain a relationship with.  There are no simple formulas. You must not try to analyze or change her..that is just another rejection from her point of view.

The best thing to do is to be straight and somewhat sympathetic without being drawn into any manipulations that will make you angry. You have to have very clear boundaries..take care of yourself, and be with her as much as you can without getting engtangled in her inner life.

If there is an opportunity to recommend therapy, that is the best you can do.