The principal of Merion Mercy Academy abruptly announced her resignation on Thursday, days after a student wrote an online letter saying that Margie Winters, a former teacher who was fired in 2015 from Waldron Mercy Academy for being married to a woman, had been unceremoniously escorted off the Merion Mercy campus last week.

In an email to the Mercy community, Sister Barbara Buckley said Friday would be her last day.

"This year has been a challenging one for our cherished Merion Mercy and I am deeply saddened by any hurt I have inadvertently caused," the 64-year-old nun wrote. "Many complex issues have arisen."

She did not address any specifics.

A letter and petition with more than 1,200 signatures from senior Zenia Nasevich outlined several incidents over the last two years at the school, including a physical fight between two girls the day after the presidential election and "a racially charged video" that went viral within the school community.

"What makes these already troubling experiences all the more frustrating is that it is like playing  a game of chicken between the students and the administration, wondering who is going to say something first, which does nothing to further the conversation about problems that are relevant to us," she wrote last week.

After Winters was abruptly forced to leave the school on April 25, Nasevich posted: "I have reached my breaking point."

Winters, the former religious director at Waldron Mercy, came to Merion Mercy to be interviewed by a group of juniors for their project on homelessness. The private Main Line schools that have adjacent campuses in Merion, Waldron is for students in kindergarten through eighth grade, and Merion is a high school for girls.

Nasevich wrote that Winters was "escorted out of the building" despite having a visitor pass and permission from the chair of the theology department.

"The project had nothing to do with her sexuality, and the harshness with which she was treated is uncharacteristic of what one would expect from an accredited Mercy school," she wrote.

A school spokeswoman did not provide additional details on Buckley's departure. Andrea Vettori, Winters' wife, said neither of them wanted to comment. Nasevich could not be reached for comment.

William Githens, chair of the Merion Mercy board of trustees, said in a letter, "Today is a difficult day for all of us who are part of the Merion Mercy community. After 25 years of extraordinary dedication to our beloved school, Sister Barbara Buckley, Head of School, has submitted her resignation. The Board respects her decision and on behalf of the entire Board, I accepted her resignation on the evening of May 2."

He also said, "This is a sensitive time for all of us at Merion Mercy. We have a responsibility to our community and our ministry to listen with our ears and open our hearts as we move forward together."

Sister Buckley's biography was still on the school's website on Thursday. It said she had been principal since 2007 and formerly had been an English teacher and administrator at St. Maria Goretti High School when it was an independent school in South Philadelphia. She has a master's degree in journalism from Temple University and a master's in organizational development from the University of Pennsylvania.

In her letter, she said that after "prayerful considering, I believe that now is the time for me to step down. There is never a good time, and it is never easy, but having been here for 25 years, I am confident that our school is on a path to even greater success and has a very strong administrative team in place."

Some of her team's accomplishments, she said, included creating a program to support underdeveloped communities around the world, and developing a nationally acclaimed rowing program.

Winters was fired in June 2015 after some parents found out that she had been in a same-sex marriage since 2007, setting off an uproar that cast national attention on the small private school and divided parents. Supporters petitioned the Archdiocese of Philadelphia to reinstate the well-liked teacher but Archbishop Charles J. Chaput said the Sisters of Mercy who run the school showed "character and common sense" in firing her.

Supporters formed Stand With Margie, which now works on LGBT inclusion in the Catholic Church. Winters' story was highlighted by the U.S. Human Rights Commission, which invited her and Vettori to the White House for a welcoming ceremony for Pope Francis in 2015.