Ugh turmoil at work...HOW DO I SHUT SOMEONE UP?!?

As most of you know, my boss got canned yesterday. So I've been assigned to work for someone else, but I don't know what I'll be doing yet. Anyway,this guy already has an assistant, who just found out I'll be joining her (I don't know what capacity though), and she's FREAKING OUT. Comes into my face and says 'I WILL NOT work under ANYONE else!!!!'.

She is a lazy, egotistical, STUPID person, who has no clue as to how to work in this business, or what it's even about. She's only here to push her own material, and wait to be discovered. I however, KNOW the business, went to school for it! So she's feeling threatened now, and starting TROUBLE.

HOW DO I GET THIS RAG OUT OF MY FAAACCCE!
I already told her to dial it down a notch and wait for the bodies from the layoff to clear before she starts on her TIRADE!