Stay away! Stefanie is a very cool and friendly person, but totally flaky and disorganized. She doesn't really seem interested in the class she's teaching so much as using class discussion to help her own thesis work. She was often late to class (sometimes as much as half an hour) and once cancelled class for personal business.
Actual class discussions were pretty good though, but you expect a bit more from your TA, and I didn't feel I got much out of having her. On the other hand, she's a VERY easy grader, and her unreliability means she accepts late papers.