The civil suit, filed by attorney Tim McGowan, says Winfrey "launched what amounted to a defamatory campaign" against Mzamane late last year by implying that Mzamane is "untrustworthy, failed the students of the academy, did not care about the students at the academy, knew of alleged physical and sexual abuse at the academy and participated in a cover-up of the alleged abuse," according to legal papers.
The suit cites Winfrey made last October and November in the wake of a dorm matron at the school being charged with assaulting and abusing students.
Mzamane, 39, also filed a defamation suit against the blog the Huffington Post and publicity expert Joan Stewart for a Nov. 19, 2007, posting by Stewart saying Mzamane was charged in connection with the scandal.
Mzamane has said there was no cover-up at the school and she knew nothing about the allegations, which she learned about while on a business trip to the U.S.
Seeks Quarter Million, Plus DamagesMzamane was the assistant head of operations at a private school in Philadelphia when she says Winfrey recruited her to run the Oprah Winfrey Leadership Academy for Girls. She started work on Dec. 31, 2006.
Since her termination, Mzamane has not been able to find comparable work and suffers from "depression, anxiety and insomnia," the suit states. She is asking for $50,000 for each of five different claims, including defamation by innuendo and intentional inflection of emotional distress, plus unspecified punitive damages.
A rep for Winfrey did not immediately respond to a request for comment, and neither did the Huffington Post nor Joan Stewart.
A trial for the , Virginia Makopo, will resume on Wednesday, Oct. 8. She has pleaded not guilty to abusing and assaulting six girls.
's South African , filed a defamation lawsuit against the TV star in Philadelphia Common Pleas Court Friday in an attempt to salvage her professional reputation, PEOPLE has learned exclusively.