The girlfriend of Oscar nominated actor JONAH HILL is hiding a secret druggie past!

Sources say actress Isabelle McNally, 24, battled a cocaine addiction that got her booted out of several elite New York City schools.

“What Jonah might not know is that Isabelle struggled with a coke problem before she cleaned herself up,” a friend told The ENQUIRER.

“That may be important to Jonah if he considers Isabelle marriage material.”

Ironically, in his Oscar-nominated role in “The Wolf of Wall Street,” Hill plays an out-of-control druggie who snorts cocaine and uses quaaludes, a sedative. The portly 30-year-old actor, who also won acclaim for his role in “Moneyball,” met Isabelle last September.

She’s now filming the pilot for HBO’s drama “The Money” with Ray Liotta. Isabelle has also appeared in the films “Indigo Children” and “Frances Ha.”

But back in 2006, a report on the celebrity website Gawker. com claimed that Isabelle – daughter of famed New York City restaurateur Keith McNally – was kicked out of several elite private Manhattan schools due to her “nasty habits.”

The site also claimed Isabelle boasted on her “MySpace” web page that she was a “proud member of Narcotics Anonymous.”

Since then, Isabelle has apparently straightened up. She and Hill have been spotted walking their dogs in West Hollywood, holding hands while shopping for groceries and even eating lunch in matching outfits.

Hill previously dated his high school sweetheart, Jordan Klein, for nearly four years and was linked to Dustin Hoffman’s daughter Ali for nine months in 2012.

“Jonah should be wary,” said another pal. “Isabelle definitely has the capacity to lead him down a dangerous path.”