mobbing
Mobbing is a term used to describe group bullying in which one or more employees covertly attack another.  Mobbing and bullying consist of psychological and emotional terrorism in which the target or victim is driven into a helpless position.  One person—the victim--becomes the focus of scapegoating, rumor, and innuendo.  The victim is badgered, intimidated, and humiliated. This occurs through persistent, targeted, hostile behavior (verbal and nonverbal) designed to undermine the integrity of the victim.  Deprecating rumors are created.  The goal is to ostracize, isolate, and eliminate the victim. Offenders participate in character assassination, humiliation, and disruption. 
After being victimized at work by mobbing, she left work and went into a deep depression.