Lindsay Lohan drank, giggled as she tweeted drug confession

Although Lindsay Lohan sounded remorseful in her September 17 Tweet, where she admitted to failing a drug test, a witness has revealed that the star laughed and quaffed as she crafted that statement on her Blackberry.

The witness also said that the Mean Girls star typed her confession that night at Hollywood eatery Magnolia.

Lohan composed her missive as her assistant and a male pal coached her on how to make it "more personal," the witness recounts.

"Her friend would say, 'No, use 'setback,' don't say 'mistake.' They'll say you make mistakes all the time!" The friend went on, "It's better to say you're responsible. Denying it will just get everyone mad per usual," Usmagazine.com quoted a witness as saying.

Lohan's response: "She giggled" and had her assistant order her another Jack and Coke, according to Magnolia spy.

Once the final copy was sent off to her management team - Lou Taylor and Larry Rudolph, who famously helped Britney Spears clean up - Lohan wasn't "emotional," the witness added.