Is it true that Winfrey "refuses to allow union representation of any sort inside the doors of her studio?"
Doesn't look like it. Meet 74-year-old Delores Olofson, an SEIU member profiled in the SEIU newsletter, Stronger Together [WARNING: pdf], from the Summer of 2005:
Olofson works part-time in Guest Services at the Harpo Studios, where Oprah is taped. Her main responsibilities are checking guests' i.d.'s and hanging their coats. She has been a Local 1 member for more than a decade and a steward for eight years.