More often than not, fake friends are narcissists. They have trouble forming real connections because they are incredibly focused on themselves. Healthy friendships are about give and take, but a fake friend will take all of your attention and give you nothing in return.
Emotionally unstable people do not always make the best friends. While being supportive to your friends is incredibly important—especially if they are struggling with something—fake friends will take advantage of your willingness to listen. They will take you on an emotional roller coaster without any concern for your needs.