BEHIND her brave smile, SANDRA BULLOCK is facing a devastating drug heartbreak.

Insiders close to the Oscar-winning actress say she’s distraught over news that the teen daughter of former husband Jesse James, Chandler, is battling an addiction to crystal meth.

“This has been an absolute nightmare for Sandra,” said a close source. “She considered Chandler to be like a daughter when she was married to Jesse. And Chandler loved Sandra like a mother – that’s how close they were.

“When Sandra heard about Chandler’s addiction problem, she was crushed. She was also furious with Jesse. As her father, Sandra thinks he should have been keeping an eye on her. But he didn’t.

“All of Chandler’s friends in Austin were aware she was struggling with a terrible drug problem – and Sandra wants to know why Jesse, her own father, didn’t seem to know it.”

The teen checked into rehab in April for drug addiction, seeking help at an undisclosed facility after reportedly abusing several substances, including methamphetamine and keyboard cleaner.

Earlier this year, photos emerged of the 18-year-old inhaling what appeared to be crystal meth at a party. In an e-mail statement to the 44-yearold West Coast Choppers owner and “Monster Garage” star confirmed that Chandler had spent the month of April undergoing treatment. He added that she’s now attending Alcoholics Anonymous meetings and working through the 12-step program.

Sandra, 48, who has known Chandler since she was a little girl, was heartbroken when she found out about the teen’s troubles, says the source.

“Sandra was crying her heart out,” the source continued. “She’s also worried sick that, somehow, the effects of her divorce from Jesse may have had a terrible impact upon Chandler…that she spun out of control after that.

“Sandy can’t help wondering if things had turned out differently for her and Jesse, this might never have happened.” Chandler, whose mom was Jesse’s first wife, Karla Huber, is the oldest of Jesse’s three children. He also has a son, Jesse Jr., with Karla, and a daughter, Sunny, from his second marriage, to porn star Janine Lindemulder. The tattooed troublemaker married America’s sweetheart Sandra in 2005.

“The Blind Side” star adopted her son Louis in January 2010, just a couple of months before she found out that Jesse had been cheating on her with inked stripper Michelle “Bombshell” McGee. They split in March 2010 and their divorce was final by the following June.

Hoping that the fourth time’s the charm, Jesse married billionaire heiress Alexis DeJoria in an extravagant and expensive affair in Malibu in March.

“Sandra’s heart really goes out to Chandler right now,” the insider added. “She really hopes the girl will be able to stay clean and sober. But for now, Sandra is taking this whole thing really hard.”