Don't give up on her yet, Lil_G. My dad is the VP of Human Resources for his company, and it sometimes takes his staff a while to call people back due to their workload. Many times, they are out on business trips for several days and will wait to make phone calls until they return. Or, if they have a large project in the works, they'll wait until it's completed so that they have uninterrupted time to devote to an interview.
If I were you, I'd give her a couple of days before calling again. Or, is there anyone else in the department that you could call and speak with in lieu of the original woman?
Good luck!!