A federal judge this week refused to dismiss the suit filed by Winfrey's ex-headmistress, paving the way for a March 29 trial in Philadelphia. The billionaire talk show host, as a named defendant, must be in court and has rearranged her TV production schedule to do so, her lawyers said in a recent court filing. She also appears likely to be called as a witness. After the abuse complaints surfaced in 2007, Winfrey said she had “lost confidence” in headmistress Nomvuyo Mzamane and was “cleaning house from top to bottom.” A dormitory matron who worked under Mzamane was later charged in South Africa with abusing six students.