difficult coworker

rn that i supervise appears to be passive-aggressive,does not talk to me,is very critical of my supervisory role and what i do. is very vocal to other staff members.last shift was very verbal and loud with comments about my role.(in front of staff,md)she will not discuss this with me or my director.she claims i am harrassing her.she has accused me of being racist(she is asian),not doing my work(plus other complaints).i have gone to admin but my manager does not handle conflict very well.this behavior is consistent over the last 21/2 yrs.i have adequate documentation for my files.on numerous occaisions i or my director have tried talking to her. for the most part she yells,cries,and is very hysterical. it is not in the hands of human resources. her behavior is disrupting the unit and pt. care. i have never experienced this type of behavior before and don't know how to protect myself.my director is leaving and appears not to want to be involved. i may very well end up working everyday with this rn. i don't have a problem with her,she has one with me and won't settle/negotiate any peace. please give me some advice.i have worked in critical care areas for years and never run across this type of behavior in the past. thanks!