We've all had them, that one friend who feels like more trouble than she's worth... the one you know you should drop but for some reason keep hanging on to, despite the emotional strain she puts on the rest of your life.
This article discusses such friends as "Emotional Manipulators" or "Covert Aggression."
It lists and discusses these as ways to identify such people:
Furthermore, This article: Psychopaths in Sheep's Clothing elaborates on the ideas and discusses various types of aggression and the process of victimization from these types of people.
It's very interesting and hopefully an eye-opener for those of you who have these kinds of friends.
I luckily cut mine out a couple years ago and let me assure you, life got a lot easier and more enjoyable! Once you cut out the bad seed you can develop healthier relationships with your other friends since you are not always "dealing with" that "one" friend... also you can meet new friends who are amazing and brighten your life.