06/16/2008 at 05:00 PM EDT
has only been the set of her new movie Labor Pains
for a week, but so far she's earned high marks for professionalism as she gets her film career back on track.
"We were a little bit reluctant to work with her," Lati Grobman, one of the producers, tells PEOPLE. "But she's been amazing."
Lohan, 21, whose movie career has been stalled by several stints in rehab
, showed up for work June 9 on the L.A. location and has consistently been early and well-prepared for the grueling 12-hour shooting days, says Grobman.
In her return to comedy, Lohan plays a publishing house employee who escapes getting fired by pretending to be pregnant.
"She's so natural at what she does. I've never seen one take where she's off," says Grobman. "The difference between her and the other girls that are naughty in the business is that she's actually talented. It's not [like] Paris Hilton
and the rest of them. We took the chance. It's good that we did. So far, so good."
The only problem is the horde of photographers who have infiltrated the Los Angeles-area locations.
"Paparazzi are ruining my life," says Grobman. "This is the most insane thing I've ever seen in my life. They do things that are very, very aggressive. I'm not a producer anymore, I'm a police woman."
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