The `Scream 4` actress had been dating `Glee` star Chord since they met at Coachella in 2011, but they initially parted in January.
They rekindled their romance in April, but sources say they are now breaking up for good.
A friend told Star magazine: "They`re done. The last few weeks have been really rough."
Cracks appeared to be showing in Emma, 21, and 23-year-old Chord`s relationship earlier this month, when they both attended the Nylon Young Hollywood party.
The source added: "They posed for pictures. After that, the two were on opposite sides of the VIP section. It`s a really immature relationship. All they did was fight."
Before the couple had got back together, they were both thought to have moved on with Emma - niece of Hollywood star Julia Roberts - rumoured to be dating a young British man named Kasper Hogan, while Chord was pictured with TV actress Carlson Young.
When they split for the first time, a source said: "They`re just on two different paths in life. They just grew apart and decided to part ways."