Britney Spears is rumored to be opening the MTV Video Music Awards.The 'Toxic' singer - currently working on her comeback album after a two-year break - is planning a surprise performance at the Las Vegas ceremony on September 9. A representative for MTV said: "I cannot confirm or deny it."Britney, 25, has shocked fans with her recent behaviour. After divorcing husband Kevin Federline, the mother-of-two has gone off the rails, indulging in wild partying, shaving her head, attacking the paparazzi and ruining designer clothes at an OK! magazine photo shoot. Her mini-comeback tour was criticised after Britney lip-synched to her past hits.Meanwhile, a close friend of Britney's, known only as Jeff, has defended her against allegations of drug taking and being a bad mother to sons Sean Preston, 23 months and Jayden James, 11 months.Jeff said: "Britney does NOT do drugs!"Anyone close to Britney knows that she's an angel when it comes to being a mom and a friend."Her kids are everything to her, there's no doubt about it."