The 22-year-old singer, who based new album 21 on a painful break-up, said that she cannot understand how former couples stay in each others' lives.
She told Celebs On Sunday, 'I've never got that whole 'stay friends with your ex' thing.
'If we hadn't ended on bad terms we'd still be together. Life happened and I'm more accepting of it than I ever used to be.
'I don't have a panic attack if something goes wrong anymore and I can deal with things a lot better.'
She added, 'Maybe when I'm 35 and married and with my life partner I might suggest we have a drink or something. But actually probably not even then. I'm not sure I'd trust myself.
'I wouldn't trust him with his ex so it doesn't seem like a good idea does it?'