Drew Barrymore outside the Ed Sullivan Theater for the 'Late Show With David Letterman'. New York City, USA - 15.04.09

The actress plays Jackie Kennedy-Onassis' reclusive cousin 'Little' Edie Beale in the HBO movie, which airs in the U.S. on Saturday (18Apr09).

Barrymore was determined to capture Beale's character, and hid herself away from friends and family for months so she could deliver an authentic portrayal.

She tells Starpulse.com, "I went a little insane, because I just lived and breathed her. I thought that if the crew heard me talk the way I talk, they would think I was acting when I was being her and they wouldn't believe me. They would see that it wasn't real. I only spoke to people as her and I isolated myself because she was isolated. I just tried to be her in every way I could."

And her method acting had an impact on her real life relationships - her best friend had to invite the late Beale to her wedding.

She explains, "She was getting married and sent me a letter addressed to Little Edie. It was hard, it was difficult, and very lonely, but so was she."

Source: WENN