The woman known as Star, 25, began writing to Manson, 79, and moved from St. Louis to Corcoran, Calif., in 2007 to be near him.
Manson has been incarcerated in Corcoran State Prison since his 1971 conviction for conspiracy to commit murder in what became known as the Tate-Labianca killings. Star visits Manson every Saturday and Sunday for up to five hours, Rolling Stone reported Thursday.
"People can think I'm crazy, but they don't know. This is what's right for me. This is what I was born for," she said.
She added, "I'll tell you straight up, Charlie and I are going to get married. When that will be, we don't know, but I take it very seriously."
Manson seems less convinced a wedding will occur, the magazine said.
"That's a bunch of garbage. That's trash. We're just playing that for public consumption," Manson said.