My coworker cussed me out and made a lot of accusations while 2 managers watched and allowed it to happen. How is this legal? Is it legal?

Common scenario. I work in sales. A coworker doesn't like me. Instead of talking to me about her problem with me, she lets it fester, and build, and grow until she finally erupts like a volcano. At which point she is out of control verbally. Cussing and making accusations about me while 2 managers watched and let it happen. During her rant she also made a statement of an action she wanted to do to me. Plus, there were other coworkers at the scene. I was offended, frightened, and humiliated. Along with a total lack of respect for the managers involved. And now I am forced to work with her while HR reviews the situation, How is this legal? Was it legal?