They reconciled several months later and finally married this summer (10).
Green has now spoken out about their previous split, revealing his partner struggled to cope with stardom after landing a role in the Transformers franchise and the pressures of fame took a toll on their relationship.
He tells Access Hollywood, "The reality is, she was 18 when I met her and she went through an enormous change in her life... just her career in general and going from being a girl who - when I met her, she was living in New York doing (TV sitcom) Hope + Faith and we'd go to restaurants and I was the person everybody would recognise and point and laugh at or whatever.
"And all of a sudden that turned around and she couldn't go anywhere and her name and her face were everywhere. So, she went through the natural period of, 'I'm not sure if I'm ready to be in such a settled relationship.'
"I didn't want her to feel like she was stuck because she said she wanted to be in a relationship to begin with and we just never really went in different directions. We'd say, 'Oh, let's kind of take a break and see what's going on'."