Britney Spears has checked out of rehab after just one day for the second time in a week, as estranged husband Kevin Federline seeks an emergency court hearing.The troubled pop princess reportedly called a car for herself and walked out of the Promises residential treatment centre in Malibu, California.She had been pictured at the facility with her newly shaven head on display wearing a pink vest top bearing the slogan "Delicious".Meanwhile, Federline's lawyer will try to persuade court officials to expedite the custody case involving the couple's two sons.Last week Britney managed to last just 24 hours in Eric Clapton's Crossroads rehab facility in Antigua, before prompting speculation that she may be on the verge of a nervous breakdown by walking into a hair salon and shaving off her own hair.Spears turned up at Esther's Hair Salon in Tarzana, California, and demanded that the owner shave her head. When Esther Tognozzi refused, she grabbed the clippers and did the job herself as shocked bystanders and paparazzi stared through the windows.There are suggestions that the 25-year-old had opted for the drastic makeover because she believed that lice were eating her hair extensions and was heard to say at the weekend: "I had to get rid of the lice. They were horrible."Last November, Federline filed papers seeking spousal support and sole custody of the children after Spears sought to end their two-year marriage last November.© Independent Television News Limited 2007. All rights reserved.