Greene, 25, called time on her romance with the 29-year-old Broadway actor who stars in "Spider-Man: Turn Off the Dark" because of her hectic schedule, reported Us magazine.
"They are over. Reeve seems to be fine and it was just crazy with their schedules. She knows this is a pivotal time in her career. I wouldn't say I could never see them getting back together but right now they are doing their own thing," a source said.
Greene also recently said she finds dating difficult and struggles to hold down a relationship because she is constantly travelling for work.
"I'm always here and there - everyone in my industry is - and that's why a lot of relationships are fleeting. I've gotten very good at detaching whenever I have to go away for three months, which I realise is hard on friends and kind of selfish," she had said.