18-year-old Yasmin Griffiths apparently dated Cocozza for three years while they were at school and lost her virginity to him at the age of 15.
They started to fight over Cocozza's possessive nature and jealousy issues, eventually splitting when he cheated with one of Griffiths' best friends.
Speaking about their relationship in the Sunday Mirror, Griffiths claimed that Cocozza, who has attracted criticism for his wild partying and womanising ways, was "kind", "sweet" and "romantic" before their break-up.
"Frankie just went off the edge and became this different scary person," she said. "He started smoking and got drunk most nights. He dropped out of college and got in with the wrong crowd.
"At a party I caught him with a bag of mephedrone and asked him what he was doing. He said it was fun and threw it in my face."
She added: "He'll always be my first love - I just hope he doesn't lose himself acting up to the camera, as he's actually a really nice guy."
Griffiths further claimed that Cocozza had shared with her his desire to quit The X Factor over criticism of his vocal abilities.
"Last week Frankie sent me a text saying, 'I want to get out of the show and concentrate on gigging'," she revealed. "He worries everyone thinks he can't sing."
Cocozza has been romantically linked to fellow X Factor contestant Amelia Lily and he recently admitted to having "banged" Geordie Shore star Holly Hagan.
> 'X Factor' Frankie Cocozza: 'I probably should have gone in week one'