"We were forced to file this lawsuit because we didn't get what we wanted a year ago – a public apology," her attorney, Tim McGowan, tells PEOPLE.
The all-girls school was rocked by scandal late last year – culminating in one dorm matron, Tiny Makopo, being charged with physical and sexual abuse. In the wake of the controversy, Mzamane's contract was not renewed.
On Friday, McGowan filed a civil suit in Philadelphia Common Pleas Court claiming that Winfrey "launched what amounted to a defamatory campaign" against Mzamane last year by implying that she was "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."
"Before the suit was filed, all [Mzamane] wanted was Oprah to say 'I made a mistake. This lady didn't cover up any abuse,' " McGowan explained. "[Oprah] went on TV and ruined her reputation. So she wanted her to go back on TV and restore her reputation."
(Mzamane issued a statement last November, saying she did not know about the alleged abuse.)
Life After OprahMzamane was the assistant head of operations at a private school in Philadelphia until she started work at Winfrey's school on Dec. 31, 2006. Since her termination, the suit claims, the 39-year-old has not been able to find comparable work and suffers from "depression, anxiety and insomnia."
In fact, McGowan said, the educator has had to stay with family and friends and borrow money from her family to survive because no one would hire her.
Mzamane 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 has not responded to a request for comment.
With additional reporting by LIZA HAMM