The Roar singer has spent months embroiled in a dispute over the historic Los Feliz property, which was formerly occupied by the Sisters of the Immaculate Heart of Mary.

She put in an offer for the estate, which was accepted by representatives of the Archdiocese of Los Angeles, but two nuns who used to live there accepted another bid from businesswoman Dana Hollister, who subsequently moved in.

They are all now fighting it out in court, and Perry has stepped up the dispute by filming a lawsuit against Hollister.

In the legal papers, Perry accuses her rival of taking advantage of the elderly sisters in a bid to secure the property for herself.

The papers state, "(Hollister) took advantage of vulnerable, elderly nuns, who she malevolently convinced to oppose the Roman Catholic Church."

The lawsuit was filed at Los Angeles County Superior Court last week (ends27Sep15).

A final ruling over the multi-million dollar sale has yet to be made.