I had this horrible nightmare.. what could it mean?

may be the prison has more to do with your relationship feeling tied down or committed and the break up triggered guilty emotions for leaving your girlfriend. May be the girl eating represented your ex and that maybe you felt she was being feed a line, **** or that she was getting crumbs the fact that she looked as if she knew what was about to happen may be meant you thought she saw the breakup coming or that your own thoughts are centered around that may be she see you, in her eyes differently , hard telling; but that would be my guess since I don't know the details of your break up I would say you feel some degree nor guilt, shame or remorse?