Gregorini sold scripts to both HBO and Paramount Pictures before co-helming, with Princess Tatiana von Fürstenberg, her directorial debut Tanner Hall, a coming of age story set in an all-girls boarding school in Rhode Island. Gregorini and von Furstenberg also co-wrote the independent film, loosely based on their own adolescent experiences. Gregorini said in an interview, "Naturally there are some autobiographical elements, combined with things we'd witness in boarding school, and many other parts that we made up completely. You will certainly find characteristics of both of us in each of the four main girls and if you spend even a half-hour with us, it will be very apparent to you, which girls are most like me and which ones are most like Tatiana." The film was an official selection at the 2009 Toronto International Film Festival.