Possible Clues:

• Habit wearers
• The Three Sisters, perhaps, reviewed by leading newsman in The Star
• Convent group
• Convent managers
• "Finale Ultimo" chorus in "The Sound of Music"
• "The Sound of Music" extras
• Some parochial school teachers
• Sister's insurance doesn't include Erica
• Joshua's father's sisters
• Cloister residents