Nervous!

I don't know why I am so nervous right now. I'm about to go to an "informal lecture" with a professor who teaches at Berkeley. I am not nervous about meeting this professor - she may be who I end up working with if (I mean, WHEN) I go to Berkeley - and I have many questions for her to help me in my decision-making. My archaeology prof right now says he'd be willing to introduce me to her. What am I nervous about then? Going to an informal lecture with a group of people I don't know. What is the matter with me? Really, I have some serious butterflies right now. Why am I more nervous about being with peers and colleagues I don't know than meeting a big name academic?