Paris Hilton -- My Girlfriend's Coke

8/30/2010 11:35 AM PDT

Paris Hilton -- My Girlfriend's Coke

Paris Hilton is telling her friends the cocaine Las Vegas cops found in her purse was not hers -- it was probably her girlfriend's.

Paris' close friends are telling TMZ ... Hilton now says one of her friends recently borrowed the purse in question and "probably" put cocaine inside.  Paris says she got the bag back but never checked the contents.

It's slightly different from the "It's-not-my-purse" defense, but it's the same theme.

Paris is telling friends, "I had no idea the cocaine was there.  I swear on my life."

According to Hilton, she was eating sushi at the Wynn hotel with boyfriend Cy Waits, sipping a little wine.  Paris says she was tired and Cy offered to drive her home and then return to the hotel to work.

Paris is telling friends, "It could be a setup.  Everyone knows how against cocaine I am."

And there's this ... Paris is saying she believes the cops who stopped the car were "star-struck and blew the whole thing way out of proportion."