Have you ever been in a situation where you lost your cool at work?

It's not easy. I've been through it myself. I can't keep my cool because I have Tourette's. Maybe you should tell your boss. If s/he doesn't listen, go over his/her head & tell them. Go through the CHAIN OF COMMAND until something gets resolved to your satisfaction. Don't let the coworker get away with this. She should lose her job. It sounds very intimidating-the way she acted.