Oprah Winfrey said Monday she hopes anyone found guilty of abuse at her South Africa school for disadvantaged girls will be put behind bars, but she doesn't think the scandal has damaged her personal reputation.

"I have done nothing wrong ... I don't think as a school we failed the girls ... I have only done what I thought best to protect the children," Winfrey said at a press conference in South Africa Monday morning.

Winfrey said she was initially told a girl who accused the matron of abuse had left the school because the girl's mother wanted to spend more time with her. She said girls at the school, which she visited frequently, told her they were instructed "to put on happy faces" when she was there and not complain.

Video: Oprah press conference

Video: Oprah takes questions

Winfrey said the school's chief executive, John Samuel, told her in early October that a group of 15 girls had come forward with a list of complaints including the sexual assault of one of their classmates.

She then called for an independent investigation to determine the extent of the allegations. The investigation was headed by Richard Farley, a Chicago detective who works with child abuse cases.

"My experience with child predators is that no one ever abuses just one child," she said.

Oprah said the head mistress' contract would not be renewed and promised a shake-up among staff, indicating school officials had tried to keep the facts of the case from her.

Winfrey, who has in the past spoken of the abuse she suffered as a child and campaigned for laws in the United States to protect children from abusers, said that because of the high rates of rape and sexual abuse in South Africa, she had worked to ensure outsiders would not be able to reach students at the school.

But "as often is the case, child abuse, sexual abuse happens right within the family, right within the confines of people you know," she said.

Winfrey has spoken in the past of being raped by a distant cousin at age 9 and then abused by three other men, trusted family friends.

"It has shaken me to my core ... but at the core of me is a belief that all things happen for a reason no matter the devastation, and this too shall pass," Winfrey said, when asked how the scandal has affected her emotionally. She also said learning about the allegations was "one of most devastating experiences of my life."

Though she said she was not responsible for hiring at the school, Winfrey said the screening process was inadequate and "the buck always stops with me."

Winfrey said she flew to South Africa to speak with the pupils and encourage them to come forward with their complaints: "It was a chance to break the silence." She also said that the girls directly affected by the alleged abuse are receiving counseling.

On Oct. 20, she flew to South Africa again to meet with parents: "I apologized for the unfortunate circumstance and promised changes."

Meanwhile, a dormitory matron accused of indecent assault on pupils at Winfrey's school was freed on bail Monday, hours before Winfrey was to answer media questions about the scandal.

Tiny Virginia Makopo, 27, who was arrested Thursday, faces 13 charges of indecent assault, assault and criminal injury committed against at least six students aged 13-15 and a 23-year-old at the school.

Makopo, who twisted her braids nervously and blinked back tears at Monday's court hearing, said she was "not guilty" after the charges were read during a bail hearing in Johannesburg, and the magistrate allowed her to go free on a bond of $450. She was not asked to enter a formal plea.

The school announced Oct. 17 that a dormitory matron had been suspended amid allegations of serious misconduct.

The Oprah Winfrey Leadership Academy for Girls said it had hired private U.S. and South African detectives to investigate, as well as reporting allegations to the South African police.

"It is my deepest hope that the accused is brought to justice and that this serves as a reminder that any time a child has the courage to step forward, it is our duty as adults to listen and take immediate action," Winfrey said in a statement posted on the school's Web site Friday.

Winfrey opened her Leadership Academy for Girls outside Johannesburg on Jan. 2, with celebrities such as Tina Turner and Spike Lee in attendance, as well as former President Nelson Mandela.

The lavish $40 million school was the fulfillment of a promise she made to Mandela six years ago and aims to give 152 girls from deprived backgrounds a quality education in a country where schools are struggling to overcome the legacy of apartheid.

Samuel, the school's superintendent, told reporters Monday there was now a sense of relief at the school and that life was beginning to return to normal.

"We are beginning to heal. The spirit of the girls remains strong," he said.

The Associated Press contributed to this report.