I don't think she's really expecting me to fly from Michigan to D.C. on short notice. I think she just forgot (or didn't notice) that I was halfway across the continent.

I e-mailed her as you suggested, saying that unfortunately I can't make the trip from Michigan for a while and that I am not going to be in D.C. for spring break either (which is true) - thus a gentle reminder that I'm in school and in Michigan and I can't exactly get out of either in the near future.