A nun who was involved in a lawsuit with pop star Katy Perry over the sale of a convent in Los Angeles has collapsed and died during a court appearance related to the case.

Sister Catherine Rose Holzman, 89, was a member of an order of elderly nuns involved in a dispute over the sale of their convent.

Perry had offered to buy the eight-acre property and its Roman-villa-style buildings for $US14.5 million ($18.4 million), and to relocate an adjoining house of prayer used by priests. Her bid had the approval of Los Angeles' archbishop.

But local entrepreneur Dana Hollister stepped in and attempted to buy the property from two nuns who had lived there for $US15.5 million ($19.7 million). The restaurateur wanted to turn it into a boutique hotel.

However, in 2016, a judge ruled the sale to the entrepreneur was invalid.

Katy Perry had tried to win over the nuns by singing for them. ( Tracey Nearmy: AAP )

Hours before her death, Holzman spoke to local media, decrying the ruling clearing the way for the archdiocese of Los Angeles to sell the convent to Perry.

She told Fox 11 Los Angeles: "To Katy Perry, please stop."

"It's not doing anyone any good except hurting a lot of people."

The Sisters of the Most Holy and Immaculate Heart of the Blessed Virgin Mary have owned the property for more than 40 years, but they have not lived in the convent for several years.

Perry — daughter of Protestant pastors — had tried to win over the nuns, even going so far as to stage a private performance for them, singing Oh Happy Day.

But the nuns were reportedly unimpressed by the fact Perry had to read the lyrics on her smartphone and were nonplussed by the tattoo of Jesus on her wrist.

Holzman served the church "with dedication and love for many years", Archbishop Jose Gomez said in a statement.

"I was sad to hear the news of her passing and I have offered a mass for the repose of her soul," he said.

"We extend our prayers today to the Immaculate Heart of Mary community and to all her friends and loved ones."

The nuns are involved in a dispute over the sale of a convent. ( Google Maps )

ABC/wires