She had a job to do, which was to help the viewers learn more about the candidates who want to run our country. She's always a tough interviewer. I'd rather have tough now, so we can weed out the fluff candidates who are good at giving prepared speeches and sound bites but useless at actually thinking through an issue or question.
My pet theory is that these Three Stooges had a few cocktails before the show. They had idiotic grins on their faces--check it out. I think the Bimbo was guzzling foams cause she's a coward as well as everything else.