The 24-year-old Girls Aloud singer - who has been dating American footballer Jason Bell for almost two years - insists she is happy in her relationship but doesn't feel ready to settle down.
She said: "I would laugh if I saw myself in a wedding dress. I feel too young, as strange as it sounds.
"I just don't think I'm mature enough to do that at the minute.
"But is Jason the most incredible man I've met? Of course - by a mile.
"I don't have an idea for the perfect wedding, I'm just sure that when the time comes it'll be all right. The actual wedding day is not that important, it's all about making sure you're with the right person."
The 'Biology' singer also admitted she isn't ready to have children with Jason because she is still focused on her career, but would like to start a family eventually.
She added to Britain's OK! magazine: "I want to wait until I'm at a stage when I feel like I can give my kids 100 per cent of my attention.
"I'm great with children but I love handing them back."