"Sister Catherine Rose Holzman, 89, was one of two nuns fighting to retain control over a property in the trendy neighborhood of Los Feliz, California that was formerly a convent of the Los Angeles Archdiocese, Newsweek reported".
In 2014 Perry sought to buy it for $14.5 million from the archdiocese.
The Sisters of the Most Holy and Immaculate Heart of the Blessed Virgin Mary have owned the property for more than four decades but have not lived there for several years.
Holzman was attending a post-judgement hearing in Friday when she suddenly collapsed and was pronounced dead at the scene.
During an interview in 2015, she explained: "After she spoke [about] her lifestyle, and what we have been teaching for years and our older sisters have been teaching, and what we believe in, [she] just did not fit".
"To Katy Perry, please stop".
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Hollister was ordered to pay Perry $5 million in punitive damages for interfering with the sale. "It's not doing anyone any good except hurting a lot of people".
The case had put Holzman and Callanan at odds with Los Angeles Archbishop José Gomez, who had publicly challenged the sisters in court.
"Rest with the angels our most precious treasure", the message says.
Perry's offer has the approval of Los Angeles' archbishop but has yet to gain approval by the Vatican.
Sister Callahan added: "You have stolen the property of the Sisters of the Immaculate Heart". But the Catholic Archdiocese of Los Angeles stepped in, claiming that under the 1983 Roman Catholic Church's Code of Canon Law, all Church property belongs to the local diocese, rather than belonging to priests and nuns that live in work in churches and convents. However Sister Callanan told the LA Times that she and Sister Holzman disapproved of the pop stars image.
Another of the nun's concerns is with the singer herself.