Bullying/Mobbing in Public Sector

I work for a local government as a middle manager. My duties include training and supervising junior employees. A few years ago a new employee was hired and assigned to our branch who's skills and performance were well below what was required for the job. However, she was able to continually charm myself and other staff into helping her through her workload. Over time, due to my guidance and training, her performance improved significantly (but not up to that of her peers). Meanwhile, she had also become very popular with most staff by organizing social events, remembering birthdays, socializing, etc. A warning sign I should have recognized at the time, however, was that there was always a small number of staff who had serious conflicts with her and didn't trust her.

Naively, we dismissed these incidents telling ourselves that she simply couldn't be the type of person they were describing. Another warning sign was her subtle but continual use of gossip to slowly discredit fellow employees that she considered competitors. A couple of occasions I caught her trying to discredit me to my own boss, but fortunately I had a close working relationship with him so nothing came of it and I accepted her apologies. But I was finally starting to wake up to who she really was and she knew it.

A couple years later, my boss was forced to resign due to poor health. She wasted no time going to coffee dates with the incoming boss (a nerdy guy who loved the attentions of a young, attractive female) and "educating" him on who the "problem" people were in the office. She also went to senior management claiming to be a long suffering victim of mistreatment by myself and my former boss (even though she had at one time nominated him for a "best boss" award).

She told the new branch head that I was a poor performer and lobbied for my firing and her promotion to my job. Through false allegations and slander, she gained the support of two of my co-workers who joined her in a viscious smear campaign against me, including claiming I had mental problems (a common bullying tactic I later found out) and had harrassed her by unfairly accused innocent her of dishonesty mutliple times. The new boss begain to strip me of my job responsibilities but claimed it had nothing to do with their smear campaign.

At this point, seeing my once excellent reputation in complete tatters and feeling totally isolated, I expected either firing, transfer to an inferior job, or demotion to be imminent. Each day I went to work thinking it might be my last. Luckily, I found a website about workplace mobbing and realized what was happening to me. I was also fortunate that a few long standing friends (with impecable reputations and influence) in other branches were aware of what was going on and witnessed it. They were able to provide me with advice and support and offered to testify to HR about what that they had witnessed the bullies say and do.

HR initially offered support and promised disciplinary action against the three bullies. I also provided them with info on workplace mobbing. Unfortunately, without explanation, things soon stalled and they only interviewed my bullies, myself, and only one of my supporting witnesses only after she insisted on it. And, no surprise, they concluded that it was all just a minor mishandling of issues by all involved and my allegations were largely just paranoia. My one witness was not referenced and they became very angry when I brought this up. They said mobbing may have occurred but they didn't have time to investigate it.
Nevertheless, HR and upper management realizing that I had the support from a few influential co-workers probably saved my job.

The main ringleader transferred out shortly after as did one of her allies.
Even though I hear stories of her continued use of gossip and slander against rivals and new conflicts with other staff, she has quickly won popularity with upper management in her new branch and recently won a promotion. I was fortunate that my new boss who supported her transferred to another city and I now have another excellent new boss who has known me for many years, and I have regained my status and popularity in my branch (but not the overall dept).

Looking back, I realize she initially used me to gain position and status in the branch. When she realized I was slowly seeing through her acts of deception and her gossip against her fellow workers, she turned on me as soon as she found people who she could charm and deceive into supporting her. I wonder if I would have been better off to pretend to be fooled by her like most everyone else?

I'm still subject to actions of my bully as she still works at smearing my reputation as evidenced by her friends and new coworkers who suddenly started giving me the cold shoulder. I also suffer from PTSD from the very nearly losing a very good job that I enjoy and almost losing my career. I also have ongoing fears that she or one of her allies might become my boss someday or that she'll manufacture new lies against me and renew her efforts to get me fired. Based on these websites, bullies rarely give up attacking people who they suspect are on to them.

Any advice on trying to overcome PTSD? I'm constantly in fear of a recurrence of what happened. Despite this being an excellent job with great benefits, should I look for another place of work?