The singer, who was cleared of drugs charges earlier this year, said her beliefs helped her through dark points in her life.
"I'm probably more religious and spiritual than people know," she told the Telegraph.
Despite initially taking her father's denomination and being baptised in a Greek Orthodox church she became Catholic with her mother in later life.
She said she's been going to the same church since she was young and prefers to go on her own.
"I wait until it is completely empty and light candles. The place I go to has 12 different icons, and I always go to Mother Mary, on the left-hand side, and I just sit there for half an hour and pray."
It's the first time the former N Dubz singer has spoken about her faith but she said that's because she had never been asked.
"I've never really talked about it because I know a lot of people aren't into it, and I don't want to bore...people. If they don't want to hear it, then there's no point trying to explain it," she said.
She admitted thinking speaking openly about her faith could damage her career, "It's like a personal thing," she said.