With the hours ticking down until [article id="1643969"]Lindsay Lohan reports to the Los Angeles-area's[/article] Century Regional Detention Center in Lynwood to server her 90-day sentence for probation violations, she has reportedly been a nervous wreck.

On Monday evening at 8 p.m. PT, she sent what could be her final tweet before being locked up, writing, "The only 'bookings' that I'm familiar with are Disney films, never thought that I'd be 'booking' into jail ... eeeks."

People.com, quoting anonymous sources close to the 24-year-old actress, said she had a rough weekend at the Pickford Lofts sober-living facility, where she checked in last week. "It's been a rough weekend," the source said. "She has not been able to sleep and has barely been eating. All weekend, Lindsay kept crying, chain smoking and chewing her nails."

Even frequent visits from mother Dina and sister Ali, as well as ex-girlfriend Samantha Ronson and other friends, have not calmed Lohan's anxiety about reporting for jail on Tuesday (July 20) morning.

"She is a nervous, fidgety mess, and her legal team, family and friends are very concerned about her fragile state," the source said. That anxiety was likely heightened on Monday, when Lohan made a last-minute appearance before Judge Marsha Revel and [article id="1644012"]attorney Robert Shapiro announced he was resigning[/article] from the case after less than a week.

Lohan has been trying to come to terms with the pending lockup, People.com said, but as the day drew closer she began to get anxious about spending 23 hours a day in a 12-by-8 foot cell in the segregated, protective-custody wing of a women's jail facility. "She's been picturing herself in jail and she can't handle the idea of it," said another anonymous friend. "She doesn't want to go. She doesn't think it's safe. She doesn't know how she'll make it."