When a Co-worker Snaps!

What do you do when a co-worker snaps?

My sister recently experienced a situation where the woman that she works with just went slam off in the office. The co-worker, who is known as the "crazy lady," raised her voice and started yelling at a superior in the office. She went into a tirade about why her manager could not "tell her what to do." She screamed at the lady and ran out to speak to another manager about her situation. This made my sister very uncomfortable since she sits directly beside this woman.

Now everyone knows how stress can cause bad situations at work. We even have phrases that depict this such as "going postal." Well the crazy lady came to work with a gym bag, but never works out. She has started doing things that are seemingly cries for attention. She usually wears makeup and has recently stopped wearing it. She purchased new dogs. She even has been starting arguments with other co-workers. When does this stop?

So now my sister feels like a hostage in her own workplace. She has to walk on eggshells while dealing with the crazy lady. She is scared that she may even come to the workplace and do something desperate. So what does one do in this situation?