I had people in my head with names but also knew I had created them. I couldn't get rid of them though, that's partly why I went to therapy. One's imagination can do weird things as far as symptom formation.

I also had a "group" of men, without names who said rude/ugly things to/about me; my therapist got rid of them when she told me to tell them she did not believe they existed and thinking about her small size (she was oriental) and imagining my relaying to the group what she said and the group getting angry at being told they did not exist and jumping her, I found that imaginative, convoluted, silly scenario very amusing and never heard from them again.

I think you have to start relating more to real people, ignore Sarah and the others and work to get out of yourself more. What you think about and concentrate on is where your energy will go. If other people make you anxious so you retreat into your head, you are going to meet people there that are both easier to deal with but also give you this problem of having them in there with you, confusing you and making it harder for you to relate in the real world.