The 'Starry Eyed' singer dated the Radio 1 DJ for 18 months but separated from him late last year blaming work Commitments and she now admits the pressure of being in the spotlight proved too much for them.
She said: ''I was naive to think my relationship with Greg James wouldn't be in the spotlight. I fell in love with him because he's very positive and intelligent and a really good person. I thought it would be fine, that it would last forever. That I had fallen in love with someone so purely and simply was amazing to me. It was very sad that it didn't work out and was down to factors such as not being able to see each other much.
''When I was young I would read about people who had broken up because they hardly ever saw each other and I would think, 'That's rubbish. You can always make it work if you're in love.' It's so sad to me that you can't - so much about a relationship is about being together.''
The pop star - who is returning with her eagerly awaited second album later this year - has since found love with American dubstep DJ Sonny Moore and she admits she was shocked at how quickly she was able to be in another relationship after her painful split from Greg.
She told YOU magazine: ''I became very good friends with Sonny when we worked together and after that we realised we wanted to spend a lot of time together. Although we are very similar, I didn't see it coming at all, especially after such a sad time breaking up with Greg. Sonny is based in Los Angeles but sort of lives in hotels. I've been splitting my time between my work and seeing him on tour because he pretty much does a show every night, so if I want to see him, I go along.''