Behavior of a co-worker?

Yeah, I think she needs to get some kind of mental evaluation. She could have just been having a bad day, but she could also have some kind of major personality disorder and come into work with a bomb strapped to her chest one day. If she can't get along with anyone, thinks she's better than everyone, and freaks out and lashes out when she's criticized, there's a good chance that something's wrong. Talk to your supervisor and tell her that she needs to address the issue because if something happens, it's all on her. Are there other people in the office who have a problem with this woman or her behavior? They should speak up too. Good luck.