(Corrects number in pope's name in penultimate paragraph)

By Philip Pullella

VATICAN CITY, April 24 (Reuters) - Floribeth Mora Diaz does not care if people think she is crazy. She is convinced - and so is the Vatican - that she owes her life to a miracle cure because she prayed to the late Pope John Paul.

"I have experienced the mercy of God in my own life and I am grateful," she told a news conference at the Vatican on Thursday explaining what Church investigators believe was a miracle attributed to John Paul's intercession with God.

Pope Francis will elevate John Paul to sainthood in the Roman Catholic Church on Sunday at a ceremony expected to draw more than one million people to the Vatican.

"People can say I am crazy and that's fine. I say I am a holy crazy person because I am healthy now," she said.

Mora, 50, and from Costa Rica, suffered a brain aneurysm in April, 2011. After a series of tests in a hospital, including a brain scan, and after a three-hour operation, doctors gave her the bad news.

"They sent me home and told me I had a month to live and that there was little hope," she said, speaking with tears in her eyes.

She began praying to the late John Paul, to whom she was very devoted and who died six years earlier in 2005.

"I prayed to John Paul and I asked him to tell God that I did not want to die because I love my children and did not want to abandon them," she said.

On May 1, 2011, still sick, she woke up 2 a.m. and turned on the television to watch the ceremony in St. Peter's Square where John Paul was being beatified, the last step before sainthood.

"I fell asleep and when I woke up I heard the voice of John Paul telling me "Get Up! Don't be afraid!"

She says she got out of bed, shocking her husband, and told him "I feel good".

After successive tests, including new brain scans, she said doctors were "stupefied and they had no way to explain it."

A Vatican medical commission later declared that the cure was medically inexplicable.

Mora, who said she is not concerned about sceptics, will be one of the main participants at Sunday's canonisation ceremony, where John Paul, who visited Costa Rica in 1983, will be declared a saint along with Pope John XXIII, who reigned from 1958 to 1963.

Before his beatification in 2011, the Church credited John Paul with interceding with God to perform an earlier miracle, the healing of a French nun who was suffering from Parkinson's, a disease which also afflicted the pope in the last years of his life. (Reporting By Philip Pullella, Editing by Angus MacSwan)