If she is threatening other people I think higher authorities should be involved. Is there children around when she acts like this? I realize I am not angel but I sure wouldn't want anyone acting like this in front of my kids.
I have had a similar situation. A parent come in a small school cursing loudly. The children were lined up for lunch and teachers had to lock down except for the room I was in, the parent was standing in the door way. We couldn't move out for fear she would get physical, I thought she would. The director of the school was in a meeting and didn't know anything. I talked to the director after the fact and expressed my concern. I was scared, I know the kids that saw this must have been mortified. I was told by the director to write a letter of complaint against her to the school board so they would have it on file. So that is what I did. To my knowledge there was never anymore out burst again.
For the safety of the students and parents at your school I would encourage anyone in contact with her to keep a log of her unappropriate actions just incase it does have to go to the board or God forbid to the police. Maybe if the right person calmly explains to her to calm down she will put forth more effort.
We have a mom who is continually yelling at everyone. She is a continual problem for the principal, and on Friday she cornered me (I'm not PTA pres until after the end of May!) and started off with "I know you want me out of here, and I'll be here whenever I want, no matter what anyone says. I'm watching you!"
Well, good Lord. I didn't sign up for that! I talked with the principal, and he is painfully aware of the situation, and wants to do something legally to keep her out of the building.
I hate this. I mean, I don't want my other parents to be verbally beaten, and certainly our pricipal doesn't deserve that treatment...but has anyone ever heard of banning a parent from the PTA office? I figure she can say her peace at open meetings...but I hate banning any parent from a parent/teacher organization.