I agree with letting this person know you will not participate in the childish and mean behavior. Tell them to call you by name, if they persist in calling you names, make a copy of the harrassment policy, see the HN and report this behavior, giving her a copy of the policy, if the HN does not take action, go to HR and file a complaint. Even if you are changing jobs, others will be staying and they do not need to be subjected to this type of behavior. Prayer does help, so does counselling, and it seems that this employee needs some of both. I wish you a blessed day.