The former Big Brother contestant told the Daily Star that she will not put up with infidelity, but believes her partner has put his womanising reputation behind him.
Thomas explained: "I'm one of those girls who'd walk away if he cheated. He knows that so I don't think he'll risk it! He's scared of me. He's like, 'Babe, you're so fiery', and I'm like, 'Yeah, I know'.
"I'd seen all the stories before we got together, but everyone has a past. He's made a few mistakes and it's because he hadn't found someone he wanted to be with."
She continued: "He is a sweetheart and treats me really well. He has such a big heart. He's so generous and caring and whatever he's got he'll give you. He always makes out like he's a hard man, but he's a big softie. He looks after me."
The glamour model was first linked to Defoe in July.