On the day in question, Desiree said, she started talking about religion to the other girl "when God said I've got to tell more people about Jesus."
The other girl "was sorta getting in trouble and I wanted her to get saved," Desiree said of her classmate.
Desiree's stepfather Bill Taylor and mother Brenda Taylor said they believed their daughter, and told their story to the nonprofit Rutherford Institute, an organization that defends the First Amendment right to religious expression.
They said the Rutherford Institute intervened at school on Desiree's behalf.
It was the Rutherford Institute that invited Desiree to speak today.
"When you tell a child who's in elementary school that they've broken the law because they show their faith, it's devastating to that child," said Institute Legal Coordinator Ron Rissler.
Rissler, who was involved in Desiree's case, said the institute gets more than 200 calls a week from Americans who feel they're suffering from religious discrimination.
Desiree said she feels "people should be allowed to talk about God whenever they want. You don't hear a lot about Jesus and God in public school."
Before she entered public school, Desiree went to a private Christian school. "I did it there all the time," she said.
Desiree said she "hears" God's messages in her heart. Her parents say she prays often, and has a "tender heart." The family attends Harvest Baptist Church.
Congressional members and religious rights advocates will attend today's event. U.S. Rep. Roscoe Bartlett, R-Md., has asked for a private meeting with Desiree before she gives her talk.
Desiree's speech will end with this: "The best thing about this is that the friend that I talked to at first wanted to hear more about God when I brought my Bible to school. She kept saying, `Tell me more, Tell me more, so I did.
"God planned all this out for me. He gave the Devil just enough rope to hang himself and gave me a taste of what being a missionary is all about."
Desiree said she wants to do missionary work in Papua, New Guinea and in Vietnam. "They should get saved, not because I want them to, but because they want to," she said.