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Years of club-hopping and partying finally caught up with Lindsay Lohan at Prince's post-Golden Globes party at the Beverly Wilshire Hotel in Beverly Hills.

"She was a mess," a source close to the actress tells Us. "She was stumbling and slurring: her friends had to take care of her."

Of course, it wasn't just one incident that pushed the Bobby star to check into rehab at the Wonderland Center in L.A. two days later on January 17.

"She's been out of control," says a Lohan pal. "She was doing tons of pills, drinking every night."

Though the 20-year-old actress has repeatedly denied having a problem ("I don't drink when I go to clubs," she said last year), the wild behavior has said it all.

"She was going out every night till 5 a.m., acting crazy," says a close source. "Going to AA meetings wasn't doing anything for her. She was still drinking."

Not only was her health in jeopardy, but so was her career. The troubled star had caused many pricey delays while shooting Georgia Rule last year, and as a result, the producers of her current film, I Know Who Killed Me, had to pay a high insurance premium.

On top of that, an insider says, Lohan had been tardy during the first week of filming in December and was on thin ice with her bosses, who were forced to delay shooting because of her appendix surgery. (The movie is now on hold until they receive her doctor's OK.)

"She had to get her sh-t together and get sober or else, literally, the girl could not work again," says the source.

What role did Lindsay's mother play in her daughter's decision to go to rehab? How is Lindsay's rehabilitation (which includes daily drug tests) going so far?

For more details on Lindsay's dark days leading up to rehab and how she's planning to clean up her act, pick up the new issue of Us Weekly, on newsstands this week.

Talk to Us: Do you think Lindsay can bounce back and regain control of her life and career?

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