I had a person following me but I lost here somewhere and she hasn't returned. When I try to get a new person to follow me, I get the "looks you already have someone with you" when I don't. How can I force a person with unknown whereabouts to leave me?
If your follower isn't around anymore, they most likely went home. Go back there and you should see them again, allowing you to summarily dismiss them for the cowardly and lazy follower that they are.