Work made me very angry today.

Quite a while ago, my supervisor brought in one of our direct care per diem staff to help us catch up on filing since the other two assistant supervisors and I didn't have time to do it. I wondered how/why they chose her versus someone else, but I didn't say anything. About a month ago, I had to take a 3 week medical leave. When I got back I realized they had brought in the same person to help with filing and office work. Since I have been back, the person has been coming in once a week for around 4 hours. Today, the person was working in my office (that is the only place there is room for her), and my supervisor came in. They started talking about hanging out last Friday night and the phone conversation they had and a bunch more stuff that pointed to a long standing friendship versus a working relationship. That made me very angry because now I know how she got picked instead of several other people who would have been a better, more logical chose. Also, I was promised about a year ago, that if more office work became available, that it would go to me (they made me start doing direct care, and I really didn't want to do it). Instead of giving me the work, they keep bringing in this per diem staff because she is a friend of the supervisors. I HATE my supervisor. It took everything within me not to lash out at her today. GRRRRRR