Britney Spears appeared unbothered in her first sighting since finishing rehab. The pop star was snapped riding in the passenger seat of a black Mercedes Benz G-Wagon with her feet up on the dashboard Thursday, in a pics obtained by Page Six. She wore sunglasses and had her blond hair down, as she was driven around Westlake Village and Calabasas. NORTH-SUNSET / BACKGRID NORTH-SUNSET / BACKGRID Spears, 44, checked out of rehab Wednesday and was back home by Wednesday night, TMZ reported . The “Toxic” singer was officially charged with driving under the influence Thursday, after her March 4 DUI arrest. Prosecutors in Ventura County hit Spears with a misdemeanor charge for driving under the influence of drugs and alcohol . She’ll be arraigned in court on May 4. NORTH-SUNSET / BACKGRID NORTH-SUNSET / BACKGRID The charge came after she checked herself into rehab on April 12 for substance abuse. “This was her own choice,” a source told us at the time .…