JULIA ROBERTS is so ter­rified that her niece EMMA ROBERTS is spiraling out of control she’s planning an intervention!

Emma – who’s 22 and reportedly heavily into the Los Angeles party scene – was busted for domestic violence in Canada on July 7 after allegedly getting into a bloody brawl with her boyfriend, “American Horror Story” star Evan Peters.

Julia was badly shaken by the ar­rest “and called an emergency family meeting,” revealed a family insider.

“Emma’s behavior has been out of control for a long time and it needs to stop before it’s too late. Julia is going to make sure of that.”

As The ENQUIRER revealed in April, Emma was devastated after her breakup with then-boyfriend, “Glee” actor Chord Overstreet, and she start­ed down a hard-partying path that has frightened her aunt Julia.

The “Pretty Woman” star has good reason to be worried about Emma’s troubling behavior, says the source, as substance abuse runs in the family.

In 2010, Emma’s father, actor Eric Roberts – who has wrestled with drug and alcohol problems – appeared on Dr. Drew Pinsky’s “Celebrity Rehab” show to kick his longtime addiction to marijuana. But just a year later, Eric released a video supporting the legal­ization of pot.

“Julia has all the reason in the world to intervene with Emma,” said the family insider.

“Emma has absolutely no supervi­sion. Julia told the family that she wants Emma to get help right away.”

The “Nancy Drew” star’s problem recently burst spectacularly into the open in Montreal when she allegedly assaulted her boyfriend Evan in their hotel room.

A fellow guest, concerned about the screaming and yelling, called the police, who immediately ar­rested Emma after arriving at the scene.

BUT SHE GOT A LUCKY BREAK. Even though Evan allegedly had been bitten and had a bloody nose, he decided not to press charges. So Emma was released.

The couple, who are working together on the FX series “Ameri­can Horror Story,” have reportedly patched things up. But Emma has long been dogged by rumors of dangerous behavior.

Confided the family insider: “Ju­lia’s greatest fear is that Emma will become the next Lindsay Lohan.”